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Experimentation 1

xperimentation

Cha

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Experimentation 2

Learning Objectives

Upon completion of this chapter, you will be able to:

Understand the concept of experimentation andcausality

Understand the internal and external validityissues in experimentation

Understand the threats to internal and externalvalidity in experimentation

Understand the ways to control extraneousvariables

Understand and compare a laboratory experimentand eld experiment

Understand the concept of experimental designsand deal with various types of experimentaldesigns

Understand the limitations of experimentation

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Experimentation 3

Defining Experiments

Experiments can be defned as the systematicstudy in which a researcher controls ormanipulates one or more independent(experiment) variables to test a hypothesis aboutthe independent variable.

ndependent variablesare the variables that aremanipulated or controlled by the researcher!

On the other hand, dependent variables arevariables on which a researcher has little or nocontrol over the research process, but theresearcher is keen to note a change in it withthe corresponding change in the independentvariables.

Tull and Hawkins (1!") stated that the essence ofexperimentation is the manipulation of one or

more variables by the experimenter in such a

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Experimentation 4

Concept of Causality

$e%ore detailin& experimentation, we will frst %ocuson the concept of causality, a prerequisite forexperimentation! 'e do thin&s in the world byexploitin& our knowled&e o% what cause what(Hobbs, *).

+n %act, causality is a conditional phenomenonbetween variables in the form "if x, then y!#ausality is an important aspect o% how weconstruct reality(ava--a et al., ).

There exist %our %ormal conditions %or causality/covariation, time order of occurrence ofvariable, systematic elimination of othercausal variable, and experimental designs!

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Experimentation 5

Concept of causality (Cont.)

$ovariation is the extent to which a causedvariable occurs with the causal variabletogether or vary together as the framedhypothesis under consideration! 0or example,sales (dependent variable) move upward with thelowered status o% the price (independent variable).

The second condition, time order of occurrenceo% variable, explains that the causal variablechan&es prior to or simultaneously with the causedvariable hence, it cannot occur a%terwards. 0or

example, when prices are increased on the frst dayo% the month, sales &o down on the remainin& dayso% the month.

The third condition, systematic elimination o% othercausal variables, indicates that the variable bein&

investi&ated should be the only causal explanationo% an chan e in the de endent variable.

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Experimentation 6

ome !asic ymbols an" #otations

in Con"ucting Experiments O = Observation or measurement made on

dependent variable as a part of the experiment

X =Exposure of the test unit under investigation to

independent variable or experimental manipulationor treatment

E% & 3xperimental &roup that is exposed to theexperimental manipulation or treatment

$% &ontrol &roup participatin& in the experiment

but has no exposure to the experimentalmanipulation or treatment

R = Random assignment of test units andexperimental manipulation or treatments to the&roups

M =Match of experimental group and control group

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Experimentation 7

$nternal an" External %ali"ity in the

Experimentation +% the desi&n and structure o% a study are such that

one can condently conclude that theindependent variable caused systematic

changes in the dependent variable, then thestudy is said to have a high internal validity!

On the other hand, i% the study &ives us a plausiblealternative interpretation of the observedrelationship between the independent and

dependent variable,then it is said to have a lowinternal validity!

The external validity typically refers to thegenerali'ability o% the results o% a study to other(usually real world) settin&s or populations

(4nderson 5 $ushman, 1).

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Experimentation 8

$nternal an" External %ali"ity in the

Experimentation (cont.) The problems o% the external validity &enerally

relate to the possibility that a specic, but timelimited, set of experimental conditions may

not deal with the interpretations of untestedvariables in the real world(6ikmund, ).

The lack of external validity puts a researcher ina di7cult situation to repeat the experiment %or adi#erent set o% sub8ects in di#erent time span. +% anexperiment lacks the internal validity,then thereis no meanin& in generali'ing the result of theexperiment!

(actors that are of serious concern for theinternal validity of the experiment may also)eopardi'e the external validity of theexperiment!The ma8or source o% threat to the

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Experimentation 9

&hreats to the $nternal %ali"ity

of the Experiment

History

9aturation

Testin& +nstrumentation

statistical re&ression

selection bias

mortality

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Experimentation 10


of the Experiment

*istory eect re%ers to a specifc event in theexternal environment that occurs between thecommencements o% experiment and when the

experiment ends. +n an experiment, maturation takes place when

the sub)ects become older, bored,experienced, or disinterested durin& theexperiment.

4 testing eect occurs when a pre+testmeasurement sensiti'es the sub)ects to thenature o% the experiment.

The instrumentation eect is said to be occurredin an experiment when either the measuring

instrument or the observer changes duringthe ex eriment!

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Experimentation 11


of the Experiment

tatistical regression is the tendency o% thesub8ects with extreme scores to mi&rate (re&ress)towards the avera&e scores durin& the experiment.

election bias occurs when an experimentalgroup signicantly diers from the targetpopulation or control group!

-ortality eect occurs when the sub)ects dropout while the experiment is in progress!Thesub8ects re%use to participate in the experimentbecause o% various reasons such as lack o% time, losso% interest in the experiment, and so on.

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Experimentation 12

&hreats to the External %ali"ity

of the Experiment

+% an experiment lacks the internal validity,then there is no meaning in generali'ing theresult o% the experiment.

+n other words, the internal validity can beviewed as a necessary, but not su.cient,condition for external validity (:arasuraman etal., ").

0our biases, such as reactive eect, interaction

bias, multiple treatment eect, and non+representativeness of the samples, thatseriously 8eopardi-e the external validity o% anexperiment.

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Experimentation 13

&hreats to the External %ali"ity

of the Experiment /eactive eect occurs when the respondents

exhibit an unusual behaviour knowin& that they areparticipatin& in an experiment.

nteraction biasoccurs when a pre;test increasesor decreases the sensiti-ation o% the respondent tothe experimental treatment.

-ultiple treatment e#ect occurs when aparticipant is exposed to multiple treatments!

This is 2uite obvious that the impact of previoustreatments cannot be fully erased from themind of the respondents!

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Experimentation 14

'ays to Control Extraneous %ariables

0resence of extraneous variable poses aserious threat to the internal as well as externalvalidity o% the experiment.

The %our ways to control the extraneous variable are =andomi-ation

9atchin&

esi&n control

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Experimentation 15

'ays to Control Extraneous %ariables

(cont.) /andomi'ationre%ers to the random assi&nment o%

the sub8ects and experimental treatment toexperimental &roup to e2ually distribute the e#ect o%

extraneous variables. 'hen a researcher suspects that the extraneous

variables may a#ect the dependent variable, he orshe applies the techni2ue o% -atching, whichinvolves matchin& each &roup on some pertinent

characteristics or some pertinent back&roundvariables.

'ith the help o% a tatistical control, a researchermeasures the e#ect o% extraneous variable andad8usts its impact with a sophisticated statisticalanalysis. +n this context, a statistical techni2ue suchas 4?O@4 can be applied.

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Experimentation 16

Laboratory %ersus iel" Experiment

The laboratory experiment is conducted in alaboratory or artifcial settin&. 4 researcher appliesor controls the experimental manipulation ortreatment in an articial environment!

4 eld experiment is conducted in the feld or anatural settin&. +n the feld experiment, the e#ect o%experimental manipulation or independent variableson dependent variable is observed in a naturalsetting!

The main ob8ective o% experimentation is to detect

or conrm the causal relationshipbetween thedependent variable and independent variables and2uanti%y them.

+n every study, there is a trade+o betweeninternal and external validity!

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Experimentation 17

Experimental Designs an" its

Classification 4n experimental desi&n is a sketch to execute an

experiment where a researcher is able to control ormanipulate at least one independent variable. The

experimental desi&ns can be broadly se&re&atedinto two &roups/ classical experimental designsand statistical experimental designs!

$lassical experimental designs consider theimpact o% only one treatment level o% independent

variable taken %or the study at a time, whereasstatistical experimental design considers theimpact o% di#erent treatment levels o% independent(explanatory) variable as well as the impact o% twoor more independent variables.

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Experimentation 18

(igure 2!3 : 4 classifcation o% experimental desi&ns

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Experimentation 19

Classical Experimental Designs

. *re+Experimental Design

0re+experimental designis an exploratory typeo% research desi&n and has no control overextraneous %actors.

These desi&ns are exploratory in natureand aremainly used to frame the hypotheses about thecasual relationship and that is why a detaileddescription o% these desi&ns is o% paramountimportance.

There are %our commonly used pre;experimentaldesi&ns. These are one+group, after+only design4one+group, before+after design4 non+matchedwith control group design, and matched withcontrol group design!

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Experimentation 20

(a) One+,roup- fter+Only Design

5ne+group, after+only design is the most basicexperimental design! 5ne+group, after+onlyexperimental design involves the exposure ofsingle group test unit to a 6reatment X and then

taking a single measurement on the dependentvariable 7O).

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Experimentation 21

(b) One+,roup- !efore+fter Design

5ne+group, before+after design involves testingthe test units twice! 6he rst observation ismade without exposing the test units to anytreatment, and the second observation is madeafter exposing the test unit to treatment!

6he treatment eect can be determined as thedierence between the rst observation and thesecond observation, that is, O1 O2.

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Experimentation 22

(c) #on+/atche" 'ith Control

,roup Design8on+matched with control group design involvesthe introduction of control group in theexperiment! 6his group does not receive any

experimental treatment! n this design, thecontrol group is introduced, so that it can becompared with the experimental group!

6he treatment eect can be determined as thedierence between the observations from the

experimental group that receives the treatment7O1) and the observations from the control group

that receives no treatment 7O2). Hence, the result

of interest is O1 O2.

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Experimentation 23

(") /atche" 0ith Control ,roup Design

6o address the problem of selection bias,matched with control group design involves thematching of experimental group and controlgroup on the basis of some relevantcharacteristics!

M indicates that exerimental !rou and control!rou are matchedon the basis of some relevantcharacteristics!

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Experimentation 24


1. &rue+Experimental Design

"/andomi'ation# is the key of dierencebetween pre;experimental desi&n and trueexperimental desi&n.

True experimental desi&n involves the randomassignmento% test units to the experimental &roupand various treatments to the experimental &roups.

True experimental desi&ns are commonly classifedas two+group, before+after design4 two+group,

after+only design4 and olomon four+groupdesign!

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Experimentation 25

1 (a) &0o+,roup- !efore+fter Design

6wo+group, before+after design is also known aspre+test9post+test control group design! 6hisdesign involves the random assignment of testunits to either the experimental group or thecontrol group!

6he control group is treated with extraneousvariable only and not with the experimentaltreatment! et the impact of experimentalvariable be E; and impact of extraneous variable

be U;! *ence, the impact of the experimentaltreatmentcan be computed as

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Experimentation 26

1 (b) &0o+,roup- fter+Only Design

6wo+group, after+only design is similar to thematched with control group design with onedierence in terms of assignment of units 7ortreatments< to experimental group and controlgroup in a random manner!

6his design is mainly susceptible to twoextraneous variables: selection bias andmortality!

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Experimentation 27

1 (c) olomon our+,roup Design

6o handle the problems of two supplementgroups, before+after design is supplemented byan after+only design and is referred to asolomon four+group design! 6his design is alsoknown as four+group+six+study design!

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Experimentation 28


2. 3uasi+Experimental Designs

+n quasi+experimental design, a researcherlacks full control over the when and whompart o% the experiment and o%ten non;randomly

selects the &roup members. The 2uasi;experimental desi&ns are use%ul because

these are less expensive and they save time!These desi&ns can also be used when trueexperimental desi&ns cannot be used. The widely

used quasi+experimental designs are timeseries designs and multiple time seriesdesigns!

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Experimentation 29

2 (a) &ime eries Designs

6ime series designs are like one+group, before+after design except that the periodicmeasurement is employed on the dependentvariable for a group of test units!

n the time series designs, treatments are eitheradministered by the researcher or it occursnaturally!

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Experimentation 30

(igure 2!=:Time series desi&n

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Experimentation 31

2 (b) /ultiple &ime eries Designs

n a multiple time series design, another group oftest units is incorporated to serve as a controlgroup! 6his design may be a better alternative ascompared with the time series designs sub)ect toa cautious selection of the control group!

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Experimentation 32

tatistical Experimental Designs

tatistical experimental designs involve theconduction of a series of experiments tostatistically control the extraneous variables andto measure the impact o% multiple independentvariables.

4s di#erent %rom the classical experimental desi&ns,statistical experimental desi&ns allow aresearcher to examine the impact of dierenttreatment levels of the experimental variable!

These desi&ns also provide an opportunity to

determine the impact o% two or more independentvariables. The most widely and commonly usedstatistical desi&ns are completely randomi'eddesign, randomi'ed block design, atin squaredesign, and factorial design!

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Experimentation 33

. Completely 4an"omi5e" Design

n a completely randomi'ed design, theexperimental treatments are randomly assignedto the test units! >y randomly assigningtreatments to the test units, a researcher tries tocheck the impact of extraneous variables through

manipulation of the treatment variable!

6he statistical technique applied to analyse the

result of this type of experimental design isknown as "?nalysis of ;ariance# commonlyknown as ?85;?!

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Experimentation 34

1. 4an"omi5e" !loc6 Design

/andomi'ed block design involves in randomassi&nment o% treatments to the experimental &roupand control &roup.

4 randomi-ed block desi&n is use%ul when there isone ma8or external variable, such as sales, store

si-e, or income o% the respondent that mi&htinAuence the dependent variable (9alhotra 5 >ash,).

+n %act, the randomi-ed block desi&n is acombination of randomi'ation and matching!

Thus, control variable denes groups and therandomi-ed experiment is conducted within eachgroup!

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Experimentation 35

4an"omi5e" !loc6 Design (Cont.)

? randomi'ed block design can be symbolicallyrepresented as

(or understanding the concept of randomi'edblock design, let us take a simple example of acompany that considers the dierence in sales infour dierent "price levels#!t is also believed by

the company that the geographic regions mayalso have an impact on the sales!

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Experimentation 36


6he research question may be do the regionssignicantly dier in terms of generating sales!6he second question may be do the price levelssignicantly dier in terms of generating sales!6his example can be symbolically represented as

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Experimentation 37

6he sales 7in thousands< results are exhibited inthe 6able 2!=!


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Experimentation 38

2. Latin 7uare Design

atin square designallows a researcher to control twoexternal variables (non;interactin&) alon& with themanipulation o% independent variable.

+n Batin s2uare desi&n, the test units are groupedaccording to the two external variablesconsidered in

the study. The test units are systematically blocked in twodirections provided by two external variables.

Bet us assume that another external variable "si'e of theshowroom# may provide the basis for dierence inquarterly sales 7in million rupees< of the company!

+n addition, the company has also considered one more

re&ion "south region#as the basis %or di#erence in salesvolume. The company has %our di#erent si-es o%showrooms across the country.

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Experimentation 39

Latin 7uare Design (Cont.)

6reatments 7levels of independent variable< areapplied to the cells in such a way that each levelof independent variable is applied to each cellonly onceas exhibited in 6able 2!@!

n atin square design, each cell is treated withonly one treatment level!

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Experimentation 40

8. actorial Design

+n the statistical desi&ns discussed so %ar, the eect ofonly one independent 7experimental< variableondependent variable was studied.

+n a %actorial desi&n, two or more experimentalvariables are simultaneouslyconsidered.

+n a %actorial experiment, more than one type o%independent variables are varied at a time but in a

structured way (

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Experimentation 41

actorial Design (Cont.)

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Experimentation 42

actorial Design (Cont.)

6he eect of each independent variable ondependent variable is referred to as the maineect! *ence, the impact of "dierent incomelevels# on sales and "price levels# on sales istermed as the main eect!

nteraction takes place when the simultaneouseect of two or more experimental variables isdierent from the sum of their separate eect!

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Experimentation 43

Limitations of Experimentation

Time

ost

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Experimentation 44

&est /ar6eting

Test marketin& means conductin& an experiment ina feld settin&.

Test markets are &enerally classifed into %our types/standard, controlled, electronic, andsimulated!

+n standard test market, a company uses its owndistribution channel network to test a new productor market mix variables.

+n controlled test market, a company hires anoutside research a&ency to conduct the study.

4n electronic test market&athers data %rom theconsumers who a&ree to carry an identifcation cardthat they present when buyin& &oods and servicesat participatin& retailers in the selected cities (Hairet al., ).

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&est /ar6eting (Cont.)

imulated test market is an articial techniqueof test marketing!4 simulated test market occursin a laboratory, where the potential consumers o% aparticular product are exposed to a new product orcompetitive product or any other marketin& stimuli.

session 21-23.ppt

Documents

concept of causality

ondependent variable

sales o

othercausal variables

sales dependent variable

price independent variable

knowlede o

ormore variables