A COMPARISON OF MBmIPULBTIVE DEXTERITY Ob

EDUCIBBLE MEPIITALLY RETARDED AND NORMAZ

TWELVE TO SIXTEEN YXAR-OLD BOYS

A Pield Report

Presented to

The Graduate Division

Drake University

In Partial Fulfillment

of the Requirements for the Degree

Master of Soience in Education

by

Jerry Leon Richardson

January 1964

A aOMPBRISOH OF MBPaIPULBTIV3 DEXTERITY OF

EDUCABLE MEETTALLY RETARDED AND NORMAL

by

Jerry Leon Richardson

Approved by Committee:

.&ZZzJr. Chairman

, .

; . i . -.' [, . ' 4.. ,

Dean of the Graduate Division

T A B U OF COHTZNTS

OHBPS1ER PAGE

1. IHTBODUCTIQHe * . 1

Source and Selection of Subjects . . . . . . . . 2

Defining the Eduoable Mentally Retarded . . . . 3

I10 S U R W Y O F L I T E B B T ~ O H M O T O R S K I ~ 5

Literature on Motor Skills of the Normal

Popula t ion . . . . . . . . . . . . . . . . . . 5

Literature on Motor Skills of the Retarded

Population . . . . . . . . . . . . . . . . . . 6

111, DESCRIPTIOBI OF TEST AND ANALYSIS OP DATA . . . . . 10 Deeoription o f Purdue Pegboard . . . . . . . . . 10

Teet Procedure and Analysis of D a t 8 . . . . . . 11 IV. SUMMBRY AND OONOLUSIOBS 17

Summary . . . . . . . . . . . . . . . . . . . . 17

Conclusions . . . . . . . . . . . . . . . . . . 20 B I B L I O G R B P W . . , . . . . . . . . . e . e . . e . m . . 22

A P P E W D I X . . . . . . . . . . . . . . . . * . . . . . . * 24

TABLE

LIST OF TABLES

PAGE

I. Test Performance on the Purdue Pegboard by Mentally Retarded Boys in Pontana Junior High Schools, Fontana, California . . . . . . . . 25

11. Test Performance on the Purdue Pegboard by Normal Students at Fontana Junior High School, Fontana, California . . . . . . . . . . . . . . . . . . . 27

111. Statistical Comparison of Gross Manipulative Dexterity Between Retarded and Normal Boys in the Fontana School District, Fontana, California . . . . . . . . . . . . . . . . . . . 29

IV. Statistical Comparison of Fine Manipulative Dexterity Between Retarded and Normal Boys in the Fontana School District, Fontana, . . . . . . . . . . . . . . . . . . . California 30

CHAPTER I

I1BTRODUOTION

During the last ten years vocational guidance became

an important reeponsibil i ty of the special c l a s s f o r the

eduoable mentally retarded, The need of the retarded t o

prepare f o r employment Increased as the need f o r unshilled

l abor decreased due t o teohnologioal development, a p h a s i s

waa placed on identifying aptitude8 which would help the

retarded t o be ae competitive as possible i n the remaining

unskilled l a b o r market.

Placement counselors have indicated t h a t manipulative

dex te r i ty was often a o r l t i c a l fac tor i n job placement. 1

howledge of whether o r not manipulative dexter i ty i s inde-

pendent o f in te l l igence would be of value i n vocational

guidanue. The purpoee of this study was t o determlae whether

a s ignif ioant difference i n manipulative dexter i ty e x i s t s

between educable mentally retarded boys and boys with normal

inte l l igenue,

The Purdue Pegboard was the t e s t ing device used t o

measure manipulative dexteri ty, A conparison of manipulative

dex te r i ty was made by use of a sequence of s t a t i s t i c a l

prooedures: (1) standard e r r o r of the mean, ( 2 ) standard

lEvelJP Murray, "Developing Potential S k l l l s of the Retarded, " Sec- Bview, XXIII (September, 19561, 35-3 .

2

e r r o r of t h e difference between means, and ( 3 ) a t - t e s t of the

d i f f e r ence between meanso1 The n u l l hypothesis was the suppo-

s i t i o n t h a t t he r e i s no s t a t i s t i c a l d i f ference i n t he manipu-

l a t i v e d e x t e r i t y of educable mentally re tarded and normal boys.

I. SOURCE AND SELECTION OF SUBJECTS

The sub jec t s f o r t h i s study were s tudents i n t he

junior high schools of t he Fontana Unified School D i s t r i c t ,

Pontana, Cal ifornia . Pontana, located about f i f t y mi les

e a s t o f Los Angeles, has a population of f i f t e e n thousand

people. Much of the a r ea i n and around Fontana has been

used as grape vineyards o r c i t r u s groves. However, t h e

cha r ac t e r of Fontana has been mostly a f fec ted by t he Kaiser

S t e e l Corporation which employs over 7,000 persons.

Se3ect iop the retarded Era=. A 1 1 boys, a t o t a l of

fo r ty - four , enrol led i n spec i a l c l a sses f o r t h e educable men-

t a l l y r e ta rded , comprised one group. The e t i o l o g i c a l cause

of r e t a r d a t i o n was not a f ac to r i n e s tab l i sh ing t h i s group.

Each sub j ec t had been t e s ted on t he Wechsler In te l l igence

Scale f o r Children within the l a s t two years. The scores

ranged from fif ty- two through seventy-five. The obtained mean

of t h e I n t e l l i g e n c e quot ients f o r t h i s group was 68.61.

The ages of t he subjec ts i n t h i s s tudy were measured

i n months. The chronological age range f o r t he retarded group

was 144 t o 200 months with an average age of 168.56.

l ~ . P. Guilford, Fundamental S t a t i s t i c s in a A Education (New York: M c G r a w - H I 1 1 Book Co., 1950

3

a & p n . Boys enrolled i n

Fontana Junior Htgh sohools, whose age was 144 t o 180, were

glven the Oalifornia Test of Mental Maturity. Those boys

scoring between 105 and 120 were oonsidered e l i g i b l e f o r

the normal group. A t o t a l of ninety boys met botn the age

and in te l l igenoe qualif icat ions. The scores were t a l l i e d

on a frequency dis t r ibut ion. Star t ing from a score of 120,

every second soore t o a t o t a l of forty-four was selected f o r

t he normal group.

A composite picture o f the average age and i n t e l l i -

gence quotients of t he two groups appear i n these resu l t s :

k a IIQ,

Retarded Group 168.56 68.61

lqormal Group 164.34 111.14

11. DEFINIHG THE EDUOQBLE ME1Ql?ALLY REWRDBD

IN THl3 FOHTdna SCHOOL SYSTEM

The Policy of the Fontana Unified School D i s t r i c t ,

Fontana, Oalifornia, has been t o consider those students

scoring between f i f t y and seventy-five on the Wechsler

In te l l igence Scale f o r Children as educable mentally retarded.

If parenta l oonsent was given, the student was placed i n a

spec ia l olase.

General characteristics of behavior have been l i s t e d

f o r the mentally retarded. However, no cha rac te r i s t i c has

sharply dlstingulshed the educable mentally retarded from

the borderline o r d u l l normal individual. The mentally

4

retarded are regarded by Hegge as "eseential ly normal people

whose output of mental a b i l i t y places them a t the lower end

of a d i s t r ibu t ion of normal t r a i t aen l A defini t ion of mental

re ta rda t ion suggested by Sarason has been used t o define

the educable mentally retarded i n the Fontana school system.

Mental retardation re fers t o individuals who, f o r temporary o r long standing reasons, function in t e l l ec - t u a l l y below the average of t h e i r peer groupe; but whose social adequacy i s not i n question or, if' it is i n question, there I s the likelihood that the individual can learn t o f c t ion independently and adequately i n the community, h

IT, 0 , Hegge, nPs~ehologlcal Aspects of Mental Retardation, n V t a t i o q F- ketarded, ed, S, ashington : Gove-ent Pr in t ing Office, 1950).

2seymour B. (&J&~Q a A =, ed. Cliffs, New Jerseyt

QHBPTER I1

SURVEY OF LITEFUTUIE ON MOTOR SKI-

Determining the relationship of intelligence and

motor ability had been the object of various investigations,

Early studies were based on populations with normal intel-

ligence, Braoe reported that studies conducted prior to

1932 indloated little or no correlation between intelligence

and motor ability in the general population for normal

persons,1 Before this time, little effort was made to

identify the educable mentally retarded. Studies comparing

motor ability and mental retardation would have had to use

eubjects from an Institutional population,

1 LITERATURE OBI HOTOR SKILLS

OB THE BORMAL POPULBTION

More recently McCloy and Young found no relationship

between motor ability and intelligence using subjects with

normal intelligence.

Almost no relationship has been found between Intel- ligence quotients and measurements of physical ability. For an indication of ability in physical skills, intelligence quotients are useless scores, at least within the zone of intellectual n nnality that is maintained in the public achools. 8

ID. K. Braoe, "Why Physical Education is a Way of Education," Jourmal of Health and Physical Education, I11 ( De cember , lwr20=53- -

2 ~ . H. McOloy and Norma Young, Tests and Measurements in Phssioal Bducation (New York: Appleton, Oentury, and =fts, 1 9 5 4 ' ) m .

6

Using the Johnson Physical S k l l l Test, Keller drew a

s i m i l a r conclusion. The f lndings indicated t h a t motor a b i l l t y

increases with chronological age, but not wlth mental age o r

In t e l l i gence ~ u o t i e n t . l

Testing 8ubJects from a normal population, Goodenough

found a low-positive relationship between react ion speed and

scores on in te l l igence t e s t s .* l o consistent d i f ferences

appeared i n reaotion speed between children from the upper

and lower socio-economic classes.

11. LITERATURE ON MOTOR SKILLS

OF THE RETARDED POPUUTION

The opinion expressed by re la ted l i t e r a t u r e has been

that a significant difference i n manipulative dex te r i t y

ex i s ted when a comparison was made between normal and mentally

re tarded children. Discussing the mentally retarded, Tredgold

wrote, "Even the best o f them ra re ly a t t a i n t o the precision

and neatness of movements which the ordinary well-trained

ch i ld i s capable. "3

l ~ i n d s e ~ D. Keller, "The Effect of Maturation on Physical S k l l l as Measured by the Johnson Ph s i c a l S k i l l

n Test , Research Quarterly, I X (October, 1938 3 , 54-58.

2Plorence Goodenough, "The Development of the Reactive Process From Early Childhood t o Maturity," Journal a

~ e r u n t a L p s y c u l o a , X V I I I (1935) 1 4 3 1 - 4 5 0 .

3 ~ . F. Tredgold, A J'extbook of Mental D (Baltimore: The Williams and Wilkins Company,

7 Along the same l i n e , Goodenough believed the mentally

re tarded were typ ica l lp awkward and clumsy i n t h e i r movements.'

Sloan concluded tha t the mentally retarded were s ign i f i can t ly

i n f e r i o r i n motor a b i l i t y t o children of normal in te l l igence. 2

However, according t o Hollingsworth, although it was the

exception, the mentally retarded exceed some normals i n motor

a b i l i t y . 3

Studies, c o n ~ a r i n q potor ab i l i t y . Studies comparing

normal and mentally retarded children gave evidence t o the

opinion expressed i n the l i t e r a t u r e of a posi t ive re la t ion-

sh ip between in te l l igence and motor a b i l i t y . I n a comparison

of motor s k i l l s of mentally retarded and normal chi ldren,

Howe found the normal group achieved consis tent ly higher

scores than the retarded group on each t e s t of a ba t te ry of

eleven t e s t s of motor a b i l i t y . H e s ta ted "The differences

were s izeab le and a l l were s ign i f ican t a t the f i v e per cent

l e v e l of confidence. n4

I n a study by Francis and Rarich, 284 mentally retarded

boys and g i r l e were given a bat tery of eleven t e s t s of

l ~ l o r e n c e Goodenough, ~~~~1 Te;;&:j3(Nex York: Rhinehart and Oompany Inc., 19 9 , p.

2 ~ i l l i a m Sloan, " ~ o t o r Prof iciency and Inte l l igence, " icap a m a L p~ Xental DeficiencY, LV ( J a n ~ r ~ s 1951) P -

3 ~ e t a S. Hollingsworth, !Che P S Y C ~ O ~ O K Y 5 Subnoma: u d r e q , (New York: The Macmlllan Company, 192 ) , p . 13

4 ~ l l f f ord C. Howe, " ~ o t o ~ Oharacteris t ics of Mentally Retarded Childreg (Unpublished Doctor's Disser ta t ion, The University of Iowa, Iowa City, 1958).

8

motor a b i l i t y * Data obtained from these t e s t s were oompared

with published norms based on populations of normal children.

The authors suggested a s ignif icant lack of motor a b i l i t y

In t he mentally retarded.

The mentally retarded chlldren I n t h l e invest igat ion were markedly i n f e r i o r t o normal children i n a l l motor performance t e s t s and as age Increased t 4 deviatlons from the normal tended t o become greater.

However, they concluded tha t the motor a b i l i t i e s of the

mentally retarded followed developmental curves s imilar t o

normal children a t lower levels .

Measurements of manipulative dexter i ty were made by

Cantor on a group with an upper in te l l igence quotient of

The r eau l t s indicated a marked l n a b i l l t y by subjects

of the group t o perfom manipulative dexter i ty tasks a s

measured by the Purdue Pegboard.

There seemed t o be agreement among authors that no

re la t ionsh ip ex i s t s between intel l igence and motor a b i l i t y

i n the general population having normal Intel l igence. The

general tenor of l i t e r a t u r e concerned Kith the mentally

l ~ o b e r t J. Prancis and G. Lawrenoe Rarich, Motor m c t e r i s t i o s pf M e n t a u petarded, United Sta tes

Department of Health, Education, and Welfare, Cooperative ~ e s e a r c h Monograph NO. 1, 1960).

2~ordon N. Cantor and C. L. Stacey, "~an ipu la t ive Dexteri ty i n Mental Defectives, Journab a pental Deficiency, LVI (July-August.

9

retarded was that they have a definite lack of motor abi l i ty ,

although there was some overlapping with the normal population.

Recent studies gathering oomparatlve data gave evidence to

this opinion.

CHAPTER I11

DESCRIPTION OF TEST AND ANALYSIS OF DATA

The Purdue Pegboard, a testing device used for this

study, was designed to asslst in the selection of employees

for jobs requiring manipulative dexterity. Such jobs would

probably be routine manual labor but of an exacting nature

such as packing, sorting or assembly.

I. DESCRIPTION OF PURDUE PEGBOARD

Kinds pf measurement obtainable, Separate measures

of movements of the hands, fingers and arms, were established

for the Purdue Pegboard: (1) Right hand, (2) Left hand, and

(3) Both hands.

A separate measure, achieved by assembling pins,

collars and washers was developed. This exacting movement of

the fingers, was named Assembly test.

Test norms. Norms were established on five groups

of subjects: (1) College men, (2) College women, (3) Veterans

(men), (4) Industrial applicants (women), and (5) Industrial

applicants (men). Separate norms were not computed for

high-school students. Industrial norms were used in high-

school vocational guidance since the high school student

would succeed or fail on the job in terms of his standing in

comparison with industrial employees.

11

character ie t ics . Located a t one and of the pegboard were four cups equipped with pins, co l la r8 and

washers. T h e two outside cups each contained twenty-five

pins. The f i rs t cup r i g h t of center, contalned twenty

co l l a r s . The f irst cup, l e f t of center, contained f o r t y

washere, Two rows of holes extended from the cups t he length

of t h e pegboard,

I. TEST PROCEDURE AMD ANALYSIS OF DATA

Measures of manipulative dexter i ty on three t e s t s

were obtained: (1) Right hand, ( 2 ) Left hand, and (3) Both

hands, A cumulative score of these t e s t s was used f o r a

comparison of "gross " manipulative dex te r i ty between the

two groups. The d i rec t ions f o r t e s t administrat ion f o r

these t e s t s were followed as given i n the Examiners Manual

f o r the Purdue Pegboard. 1

wnd t e s t . The object of the Right hand t e s t

was t o t ake a pin with the r i g h t hand from the right-hand

oup, The pin was then inser ted i n the top hole of the

r i g h t hand row, The score was the t o t a l number of pins

i n se r t ed i n t h i r t y seconds.

Only one sub3ect i n the normal group scored lower

than the average f o r the retarded group. A t the opposite

lPurdue Research Foundation, 868- Manual a % n r d u &gboard (Chicago: Science Research Aseociates, 19 ).

12

end of t he range, only two subjects from the retarded group

scored higher than the average f o r the normal group. The

t e s t performance has shoym t h e s e resu l t s :

Range

Mean

&ef t hand t e s t . The tes tee was allowed t h i r t y seconds

t o i n s e r t pins with h i s l e f t hand. The t e s t ee took a pin

with h i s l e f t hand from the left-hand cup. The pin was then

i n s e r t e d i n the top hole of the l e f t hand row. The score

was the t o t a l number of pins inser ted In t h i r t y seconds.

A g rea te r degree of overlapping of scores was obtained

on t h i s t e s t than on any of the other measures. A t o t a l of

four sub jec t s f r o m the normal group scored l e s s than the

average of 13.50 pin inse r t ions of the retarded group.

Scores higher than the average of 15.82 pin inse r t ions of

t he normal group were made by seven subjects of the retarded

group. The t e s t performance has shorn these r e su l t s :

uEle& Retarded

Range 11-19 5-18

Mean 15.82 13-50

band t e s t . This t e s t measured the a b i l i t y o f

both hands working together. The tes tee picked up a pin

from the right-hand cup wlth his r i gh t hand and a t the same

time picked up a pin f r o m the left-hand cup wlth h i s l e f t

13 hand and placed the pin8 dom the rows. The t e s t e e began

w i t h t h e top hole of both rows. If the t e s t ee were l e f t - handed, the di rec t ions were changed by substituting " l e f t

handn f o r "right handn and "r ight handn f o r " l e f t handn

wherever they occurred i n the direct ions. Only the t o t a l

number of pa i r s of pins were counted. The t e s t performance

has shown these resu l t s :

u.Z@iL Retarded Range 10-16 4-16

Mean 13.18 10.70

A t o t a l of four retarded subjects scored higher than

the obtained average f o r the normal group. Only one subject

from the normal group scored lower than the average of the

re tarded group.

#core. A cumulative ecore of the three

t e a t s re fe r red t o as: (1) Right hand, ( 2 ) Left hand, and (3)

Both hands, was used f o r the comparison of "gross" manipulative

dex te r i t y , Some overlapping of scores appeared between the

two groups although the normal group averaged over e ight pin

i n s e r t i o n s per subject more than the retarded group. Only

t h r e e sub jec t s i n the retarded group scored higher than the

average score of the normal group. From the normal group

only two soored l e s a than the average of the retarded group.

The cumulative scores of the t e s t s of ngrossn manipulative

d e x t e r i t y have been shown In these r e s u l t s r

Retarded

Range 38-56 14-55

Mean 46.07 37.73 Standard deviation 3.61 7.72

A sequence of s t a t i s t i c a l procedures was used t o

ob ta in a comparison of t e s t performance: (1) standard e r r o r

of t h e mean, (2 ) standard e r ro r of the difference between

means, and (3) t - t e s t of the difference between means. The

s t a t i s t i c a l data gathered l a the sequence have shown these

r e s u l t s :

Standard e r r o r of the mean .55 normal groups 1.17 retarded group

Standard e r r o r of the difference between means 1.29

t - r a t i o of the difference between means 6.46

A t - r a t i o of 6.46 was s ign i f ican t a t the 1 per cent

l e v e l of confidence. The null hypothesis, which supposes

t h a t the re i s no s t a t i s t i c a l difference i n "gross" manip-

u l a t i v e dex te r i t y of educable mentally retarded and normal

boye, was re lec ted. The inference, with few exceptions, was

t h a t a boy with normal Intel l igence has a grea te r degree of n grossn manipulative dex te r i ty than an educable mentally

re tarded boy.

4sse- t e s t . The Assembly t e s t was used f o r the

measure of "fine" aanlpulat lve dexteri ty. The tes tee took

1 5 a pin from the right-hand cup x i t h h l s r l g h t hand and a

washer from the left-hand cup wlth h i s l e f t hand. The pin was i n s e r t e d i n the top right-hand hole. Then a c o l l a r was

picked up with the r i g h t hand. A s soon as the p in was In-

s e r t ed , t he l e f t hand placed a washer on the pin; then i t

picked up another washer. The r l gh t hand then placed the

c o l l a r over the pin on top of the washer and reached f o r

another pin t o start a new assembly. The l e f t hand placed

a washer on the pin over the co l l a r t o complete the sequence

and picked up a washer f o r the next assembly. Both hands

should be i n motion a t the same time.

The t e s t e r gave a demonstration of the sequence of

movements as the ine t ruc t ions were read verbatim. The t e s t e e

was allowed t o pract ice the required sequence of movement8

u n t i l t he t e s t e r was sure he f u l l y understood the procedure.

The t o t a l number o f pa r t s assembled i n s ix ty seconds was

t he score f o r t h i s t e s t .

Each assembly had four parts. The normal group

averaged over t w o complete assemblies per subject more than

the re tarded group. Only two subjects of the retarded group

scored higher than the obtained average o f the normal group.

811 but one of the normal group scored higher than the

average of the retarded group. Performance of the two groups

on the Assembly t e s t has been shorn i n these r e su l t s :

wJEiL Re tarded Ftangs 27-49 17-44

Mean 37.34 27 91

Standard deviation 4.80 6.81

A comparison of test performance was made through a

sequence of statistical procedures: (1) standard error of

the mean, (2) standard error of the difference between means,

and (3) t-test of the difference between means. The statis-

tical data gathered in this sequence have been shown in these

resulte:

Standard error of the mean ,75 normal group 1.03 retarded group

Standard error of the difference between means 1.27

t-ratio of the difference between means 7.42

A t-ratio of 7.42 was highly significant at the 1 per

cent level of confidence. This indicated rejection of the

null hypothesis that there was no statistical difference in

"finen manipulative dexterity of educable mentally retarded

and normal boys. The inference was that with few exceptions

a boy with normal lntelllgenoe has a higher degree of 'finen

manipulative dexterity than an educable mentally retarded

boy.

CHAPTER 1V

SUMMARY AND CONCLUSIONS

During the last ten years vocational guidance became

an important responsibility of the special class for the

educable mentally retarded. The need of the retarded to

prepare for employment increased as the need for unskilled

labor decreased due to technological development. Emphasis

was placed on Identifying aptitudes which would help the

retarded to be as competitive a8 possible in the remaining

unskilled labor market.

Placement counselors have indicated that manipulative

dexterity wae often a critical factor in job placement.

mowledge of whether or not manipulative dexterity is inde-

pendent of intelligence would be of value in vocational

guidance. The purpose of this study was to determine whether

a eignificant difference in manipulative dexterity exists

between educable mentally retarded boys and boys with normal

intelligence.

So that a comparison of manipulative dexterity could

be made, two samples of forty-four boys each were selected.

All boys enrolled in the special class for the educable

mentally retarded comprised one group. The range of intelli-

gence quotients for this group was from fifty-two to seventy-

five as measured by the Wechsler Intelligence Sumey for

18 Children. The age range, figured i n months, was 144 t o 200

months. Sub jec t s of the normal group, which was made up

of boys of a similar age, scored between 105 and 120 on the

Ca l i f o rn i a Test o f Mental Wtu r i t y .

The Purdue Pegboard was the t e s t i ng device used t o

measure manipulative dexter i ty . S e p a r a ~ measures o f move-

ments of t h e hands, f i n g e r s and arms, were establ ished f o r

t h e Purdue Pegboard: (1) Right hand, ( 2 ) Left hand, and

( 3 ) Both hands. A cumulative score of these t e s t s was used

f o r a comparison of "gross" manipulative dex t e r i t y between

t h e two groups.

A separa te measure, achieved by assembling pins, col-

la rs and washers w a s developed. This exacting movement of

t h e fingers, the Assembly t e s t , was a measure of " f inen

manipulat ive dex te r i ty .

A comparison of manipulative dex te r i ty was made by

use of a sequence of s t a t i s t i c a l procedures: (1) standard

e r r o r of t h e mean, ( 2 ) standard e r r o r o f the dif ference

between means, and ( 3 ) a t - t e s t of the d i f ference between

means. The null hypothesis was the supposition t h a t the re i s

no s t a t i s t i c a l difference i n the manipulative dex t e r i t y o f

educable mentally retarded and normal boys. A t - r a t i o of

2.58, t h e 1 per cent l e v e l of confidence, was needed t o

r e j e c t t he n u l l hypothesis.

,ElI~ht band test. The normal group averaged over th ree

19 p in In se r t i ons Per subject more than the retarded group.

Only two subject6 from t h e retarded group scored higher than

the average of the normal group whereas only one subject

from the normal groups scored lower than the average of the

re tarded group.

&ef t && t e s t . The normal group averaged s l i g h t l y

over two pin i n se r t i ons per subject more than the retarded

group. Seven subjects of the retarded group scored a higher

t o t a l of pin inse r t ions than the average of the normal group.

Four subject8 of the normal group scored a lower t o t a l of

p in i n s e r t i o n s than the average of the retarded group.

p o u m4 t e e t . The normal group averaged s l i g h t l y

over t w o p a i r s of pin Insert ions per subject more than the

re ta rded group, Only one subject from the normal group

scored l e s s than the average f o r the retarded group, whereas

f o u r sub lec t s from the retarded group scored higher than

t h e average f o r the normal group,

Qumulativa m. A cumulative score of the three

t e s t s re fe r red t o as: (1) Right hand, ( 2 ) Left hand, and (3)

Both hands, uas used f o r the comparison of "gross" manipu-

l a t i v e dex te r i ty . The normal group averaged over e ight pin

i n s e r t i o n s per subject more than the retarded group. However,

1% was noted t h a t three subjects i n the retarded group scored

a higher t o t a l of p in inser t ions per subject than the mean

of the normal groUP. A t-ratio of the standard error of

the difference between means was 6.46. This figure was

significant at the 1 per cent level of confidence indicating

rejection of the null hypothesis.

~ n i ~ d a t i v e dexteritr. A measure of the exacting

movement8 Of the fingers was uonsidered to be "fine" manipu-

lative dexterity. This measure, the Besembly test, was

achieved by assembling pins, collars and washers. Plaolng

four separate parts together completed one assembly.

The normal group averaged over two complete asserublies

more than the average of the retarded group. However, two

subjects of the retarded group scored higher than the mean

of the normal group.

A aomparison of the two groupa was made by using the

standard error of the difference between means. A t-ratio

of the difference between means of 7.42 was obtained. Thla

figure was significant at the 1 per cent level indicating

rejeotion of the null hypothesis.

11. CONCLUSION

A t-score as large as that obtained on the t-test

of the difference between means for the comparison for

both "grossn and "finen manipulative dexterity indicated a

highly significant difference in the test performance of

the two groups. The resulting inference was that a boy wlth

normal intelligence wlll perform more ably on simple tasks

of both ''gross" or "finen manipulative dexterity.

The conclusion was made that manipulative dexterity

would not usually be an aptitude which could be used for

purposes of vocational guidance.

4ecommendatiou. The data indicated three subjects

of the group of forty-four retarded boys performed as

efficiently on simple tasks of manipulative dexterity as

boys with normal intelligence. The following procedures were

recommended to improve the vocational guidance of the retarded

who do poseees a no-1 degree of manipulative dexterity:

(1) identify retarded students with a normal degree of

manipulative dexterity, (2) identify jobs in the community

requiring a degree of manipulative dexterity, and (3) eral-

uate the Job performance of those retarded students performing

simple tasks of manipulative dexterity.

BIBLIOGRAPHY

Cantor, Gordon i n Mental Def'lcienclrr , LVI

Prancle, Robert J., Rarich, Lawrenoe G. po tor Charac te r i s t i c s pg $& B e n t a u Office of Education, United S t a t e s Department of Health, Education, and Welfare, OE - 35005, Washington: Government P r in t ing Office, 1960.

Goodenough, Florence. F Test-. Hew York: Rhlnehart and Company Inc., 19 9,

Guil ford , J. Po damental S t a t i s t i c s

Hegge, T. G. "Psychological Aepects of Mental Retardation," VocstlonaL. R e b a g t a t i ~ g pg a M&g&J& Retarded, E d i t e d by S, G, DiMlchael, Washington: Government Pr ln t ing O f f i c e , 1950.

Purdue Research Foundation, e p i n u #& Purdue Pe oard. Chicago :

-Research Associates, 19 R+-

Sarason, Seymour B. P s ~ c h o l o a v a E x c e ~ t l o ~ Children a A u. Edited by William M. Cruickshank. Englewood Cliffs , New Jersey: Prent ice Hall, 1955.

Tredgold, A. B. Textbook a p e n u D e f I c I e ~ . BBltlmore: The Williams and Wilkene Company, 1952. 5 9 pp.

APPENDIX

TABLE I

TEST PERFOFWINCE ON THE PURDUE PEGBOARD

BY MENTALLY RETARDED BOYS IR

FONTANA JUNIOR HIGH SOHOOLS,

FONTANA , OALIFORNIA

la t lve Score

TABLE I

(continued)

Both Hands

Cumulative Score

TABLE I1

TEST PERFOLWNCE ON THE PUFDUE PEGBOARD

BY NORMAL STUDENTS AT

FONTANA JUNIOR HIGH SCHOOL,

FONTANA, CALIFORNIA

Both Hands

Cumulative Score

TABLE I11

Statistic

Number

S T A T I S T I C A L COMPBRISON

OF GROSS MANIPULATIVE

DEXTERITY B E T m E N

RETARDED AND N0RMA.L

BOYS I N THE FONTBNA

SCHOOL D I S T R I C T ,

FONTANA , CALIFORNIA

Standard deviation

Standard error of the mean

Standard error of a difference between means

Normal

44

Retarded

44

statistic

Number

Mean

TABLE IV

S T A T I S T I C A L COMPAXISON

OF FINE MBNIPDLBTIVE

DEXTERITY BETWEEN

RETARDED m N O R .

BOYS I N THE FONTANA

SCHOOL D I S T R I C T ,

FONTANA, CALIFORNIA

Retarded I Standard deviation 4.80 I 6.81

Standard error of the mean .75 1 1.03

Standard error of a difference between means 1.27

t-ratio 7.42