educational research: experimental studies edu 8603 educational research richard m. jacobs, osa,...

Educational Research: Educational Research: Experimental StudiesExperimental Studies

EDU 8603

Educational Research

Richard M. Jacobs, OSA, Ph.D.

Research...Research...

The systematic application of a family of methods employed to provide trustworthy information about problems…an ongoing process based on many accumulated

understandings and explanations that, when taken together lead to generalizations about problems and the development of theories

The basic steps of research...The basic steps of research...

Scientific and disciplined inquiry is an orderly process, involving:

description and execution of procedures to collection information (“methodmethod”)

objective data analysisanalysis statement of findings (“resultsresults”)

recognition and identification of a topic to be studied (“problemproblem”)

Research methods...Research methods...

QuantitativeQuantitative……collects and analyzes numerical datadata

obtained from formal instrumentsinstruments

Quantitative methods...Quantitative methods...

descriptive research (“survey research”)correlational researchcausal-comparative research (“ex post facto research”)

experimental research

experimental researchexperimental research…the researcher selects participants and

divides them into two or more groups having similar characteristics and, then, applies the treatment(s) to the groups and measures the effects upon the groups

Conducting an experimental study…Conducting an experimental study…

1. select the problem2. select participants and instrument3. selection and execution of a research plan

4. data analysis and formulation of conclusions

Types of experimental comparison…Types of experimental comparison…

1. comparison of two different approaches (A A versus BB)

2. comparison of an existing approach to a new approach (AA and ~~ A A)

3. comparison of differing amounts of a single approach (AA and a a or aa and AA)

where:

A – experimental (“treatment”) groupB – control (“no treatment,” “nonmanipulated”) group

Variable...Variable...

…a concept (e.g., intelligence, height, aptitude) that can assume any one of a range of values

Research variables...Research variables...

IndependentIndependent……an activity of characteristic believed

to make a difference with respect to some behavior

…(syn.) experimental variable, active variable, cause, treatment

DependentDependent……the change or difference occurring a

a result of the independent variable…(syn.) criterion variable, assigned

variable, effect, outcome, posttest

ConfoundingConfounding……the fact that the effects of the

independent variable may intertwine with extraneous variables, such that it is difficult to determine the unique effects of each variable

…(syn.) criterion variable, assigned variable, effect, outcome, posttest

Group experimental designs…Group experimental designs…

1. single-variable2. factorial

single-variable designssingle-variable designs…involve one manipulated

independent variablepre-experimentalpre-experimentalquasi-experimentalquasi-experimentaltrue experimentaltrue experimental

types of pre-experimental designstypes of pre-experimental designs

one-shot case studyone-shot case study

…a single group exposed to a treatment ( X ) and then posttested ( O )

one-group pretest-posttest designone-group pretest-posttest design

…a single group is pretested ( O ), exposed to a treatment ( X ) and, then, is posttested ( O )

static group comparisonstatic group comparison

X2 O…involves at least two groups ( X ), one

receiving a new, or experimental treatment ( X1 ) and another receiving a traditional, or control treatment ( X2 ) and, then, are posttested ( O )

types of quasi-experimental designstypes of quasi-experimental designs

nonequivalent control group nonequivalent control group designdesign

…random assignment of intact groups that are pretested ( O ), exposed to a treatment ( X ) and then posttested ( O )

time-series designtime-series design

O O O O X O O O O

…a single group is pretested ( O ) repeatedly until pretest scores are stable, exposed to a treatment ( X ) and, then, is repeatedly posttested ( O )

counterbalanced designcounterbalanced design

X1 O X2 O X3 O

X3 O X1 O X2 O

X2 O X3 O X1 O

…all of the groups receive all treatments but in a different order; the number of groups and treatments must be equal

types of true experimental designstypes of true experimental designs

pretest-posttest control group designpretest-posttest control group design

R O X1 O

R O X2 O

…at least two groups are formed by random assignment ( R ), administered a pretest ( O ), receive different treatments ( X1, X2 ), are administered a posttest, and posttest scores are compared to determine effectiveness of treatments

posttest-only control group designposttest-only control group design

R X1 O

R X2 O

…at least two groups are formed by random assignment ( R ), receive different treatments ( X1, X2 ), are administered a posttest, and posttest scores are compared to determine effectiveness of treatments

Solomon four-group designSolomon four-group design

R O X1 O

R O X2 O

R X1 O

R X2 O

…four groups are formed by random assignment ( R ) of participants, two groups are pretested ( O ) and two are not, one pretested and one unpretested group receive the experimental treatments ( X1, X2 ), each group is are administered a posttest on the dependent variable, and posttest scores are compared to determine effectiveness of treatments

factorial designsfactorial designs…involve two or more independent

variables with at least one independent variable being manipulated by the researcher

examples of factorial designsexamples of factorial designs

two-by-two factorial design two-by-two factorial design (four cells)

…two types of factors (e.g., method of instruction) each of which has two levels (e.g., traditional vs. innovative)

A 2 X 2 factorial design…A 2 X 2 factorial design…

Independent Variable

Group #1 Group #2

Group #3 Group #4Cells

not manipulatedmanipulated

No interaction between factors

ANo interaction between factors

Interacting factors

two-by-three factorial design two-by-three factorial design (six cells)(six cells)

…two types of factors (e.g., motivation; interest) each of which has three levels (e.g., high, medium, low)

Single-subject experimental designs…Single-subject experimental designs…

1. A – B – A withdrawal2. multiple baseline designs

3. alternating treatments designs

simple A – B designsimple A – B design…baseline measurements ( O ) are repeatedly

made until stability is established, then the treatment ( X ) is introduced and an appropriate number of measurements ( O ) are made during treatment implementation

simple A – B designsimple A – B design

O O O X O X O X O

baseline treatment phase phase

A – B – A withdrawal designsA – B – A withdrawal designs…baseline measurements ( O ) are repeatedly made until

stability is established, then the treatment ( X ) is introduced and an appropriate number of measurements ( O ) are made during treatment implementation, followed by an appropriate number of baseline measurements ( O ) to determine stability of treatment ( X )

A – B – A withdrawal designsA – B – A withdrawal designs

O O O X O X O X O O O

baseline treatment baseline phase phase phase

A | B | A

multiple-baseline designsmultiple-baseline designs…used when a return to baseline

conditions is difficult or impossible since treatment effects oftentimes do not disappear when a treatment is removed

…“multiple” refers to the study of more than one behavior, participant, or setting

…instead of collecting baseline data on one specific behavior, data are collected on: (1) several behaviors for one participant, (2) one behavior for several participants, or (3) one behavior and one participant in several settings

…then, over a period of time, the treatment is systematically applied to each behavior (or participant, or setting) one at a time until all behaviors (or participants or settings) have been exposed to the treatment

multiple baseline designmultiple baseline design

Example: one treatment for three behaviors in three settings

behavior 1 O O OXOXOXOXOXOXOXOXOXOXOXO setting #1

behavior 2 O O O O O OXOXOXOXOXOXOXO setting #2

behavior 3 O O O O O O O O OXOXOXO setting #3

the baseline remains the same…

…while the treatment is applied at other

settings

alternating treatments designalternating treatments design…the relatively rapid and random

alternation of treatments ( T1 T2 …Tn ) for a single subject but not necessarily within fixed intervals of time

T1 - T2 - T1 - T1 - T2 - T1 - T1 - T2

The concept of validity…The concept of validity…

…the experiment tests the variable(s) that it purports to test

Threats to validity…Threats to validity…

…internalinternal: factors other than the independent variable that affect the dependent variable

…externalexternal: factors that affect the generalizability of the study to groups and settings beyond those of the experiment

Threats to internal validity…Threats to internal validity…

1. history2. maturation

3. testing

4. instrumentation

5. statistical regression

6. differential selection of participants

7. mortality

8. selection-maturation interaction

historyhistory…the occurrence of events that are not

part of the experimental treatment but that occur during the study and affect the dependent variable

maturationmaturation…the physical, intellectual, and

emotional changes that occur naturally in a study’s participants over a period of time

testingtesting…refers to improved scores on a

posttest as a result of having taken a pretest

instrumentationinstrumentation…the unreliability or lack of

consistency in measuring instruments that can result in an invalid assessment of performance

statistical regressionstatistical regression…the tendency of participants who

score highest on a test to score lower on a second, similar test and vice versa

differential selection of participantsdifferential selection of participants…the outcome when already formed

groups are compared raising the possibility that the groups were different before a study even begins

mortalitymortality…the case in which participants drop

out of a study which changes the characteristics of the groups and may significantly affect the study’s results

selection-maturation interactionselection-maturation interaction…if already-formed groups are used in

a study, one group may profit more (or less) from a treatment or have an initial advantage because of maturation, history, or testing factors

Threats to external validity…Threats to external validity…

1. pretest-treatment interaction2. selection-treatment interaction

3. multiple treatment interference

4. specificity of variables

5. treatment diffusion

6. experimenter effects

7. reactive effects

pretest-treatment interactionpretest-treatment interaction…the situation when participants

respond or react differently to a treatment because they have been pretested

multiple-treatment interferencemultiple-treatment interference…the situation when the same

participants receive more than one treatment in succession

selection-treatment interferenceselection-treatment interference…the situation when participants are

not randomly selected for treatments

specificity of variablesspecificity of variables…the situation when a study is conducted with (1) a

specific kind of participant; (2) is based on a particular operational definition of the independent variable; (3) uses specific dependent variables; (4) transpires at a specific time; and, (5) under a specific set of circumstances

treatment diffusiontreatment diffusion…the situation when different

treatment groups communicate with and learn from each other

experimenter effectsexperimenter effects…the situation when the researchers

present potential threats to the external validity of their own studies

reactive arrangementsreactive arrangements…the situation when a number of

factors associated with the way in which a study is conducted interacts with or shapes the feelings and attitudes of the participants involved

Types of reactive arrangements…Types of reactive arrangements…

…Hawthorne effectHawthorne effect: any situation in which participants’ behavior is affected not by the treatment per se but by their knowledge of participating in a study

…compensatory rivalrycompensatory rivalry: the control group is informed that they will be the control group for a new, experimental study (“John Henry effectJohn Henry effect”)

…placebo effectplacebo effect: the situation in which half of the participants receive no treatment but believe they are

…novelty effectnovelty effect: the situation in which participant interest, motivation, or engagement increases simply because they are doing something different

Controlling for extraneous Controlling for extraneous (confounding) variables…(confounding) variables…

1. randomization2. matching3. comparing homogeneous groups or subgroups

4. using participants as their own controls

5. analysis of covariance (ANCOVA)

randomizationrandomization…the process of selecting and assigning

participants in such a way that all individuals in the defined population have an equal and independent chance of being selected for the sample

matchingmatching…a technique for equating groups on

one or more variables, usually the ones highly related to performance on the dependent variable (e.g., pairwise matching)

comparing homogeneous groups or subgroupscomparing homogeneous groups or subgroups

…a technique to control an extraneous variable by comparing groups that are similar with respect to that variable (e.g., stratified sampling)

using participants as their own controlsusing participants as their own controls…exposing a single group to different

treatments one treatment at a time

analysis of covariance (ANCOVA)analysis of covariance (ANCOVA)…a statistical method for equating

randomly formed groups on one or more variables by adjusting scores on a dependent variable for initial differences on some other variable

Data analysis and interpretation…Data analysis and interpretation…

for single-subject research…a visual inspection and analysis of

graphical presentations of results…focuses upon: adequacy of the design;

an assessment of treatment effectiveness (clinicalclinical vs. statistical significancestatistical significance)

Mini-Quiz…Mini-Quiz…

True and false…

…experimental researcher is the only type of research that can test hypotheses to establish cause-and-effect relationships

True and false…

…the manipulation of the independent variable is the one characteristic that differentiates correlational research from other types of research

True and false…

…an experimental study is guided by at least one hypothesis that states an expected causal relationship between two variables

True and false…

…the “experiment” in an experimental study is conducted to conform or disconfirm the research problem

True and false…

…experimental research has both random selection and assignment whereas causal-comparative research has random selection not assignment

True and false…

…it is correct to state that a control group always receives no treatment in experimental studies

True and false…

…in an experimental study, the researcher makes every effort to ensure that the two groups start as equivalently as possible on all variables except the independent variable

True and false…

…in an experimental study, the researcher collects data on the independent variable from the groups to determine whether there is a significant difference between their performances

True and false…

…in an experimental study, the researcher endeavors to make the groups as similar as possible so that the only major difference between them is the treatment variable(s) manipulated by the researcher

True and false…

…even though experimental research is the only type of research that can truly establish cause-effect relationships, it is not universally appropriate for all research problems or studies

True and false…

…an experiment is valid if results obtained are due only to the control variable and if they are generalizable to individuals or contexts beyond the experimental setting

True and false…

…internal validity focuses upon threats or rival explanations that influence the outcomes of an experimental study but are not part of the independent variable

True and false…

…if a study’s results cannot be replicated in other settings by other researchers, then the study has low external reliability

True and false…

…to conduct a valid experiment, all the researcher has to do is to maximize internal and external validity

True and false…

…true experimental designs control for all sources of internal and external validity

True and false…

…the more narrowed and controlled a research situation is, the less realistic and generalizable it becomes

True and false…

…a study that is not internally valid is worthless

True and false…

…the longer a study lasts, the more likely it is that history will be a threat to the study’s internal validity

True and false……the way a researcher controls for selection-

maturation interaction is to select a design that controls for potential problems or to make every effort to determine if selection-maturation interaction is operating in the study

True and false…

…pretest-treatment interaction makes a study’s results generalizable only to other pretested groups

True and false…

…the seriousness of pretest-treatment interaction threat is dependent upon the research participants, the nature of the independent and dependent variables, and the duration of the study

True and false…

…even if intact groups are randomly selected, the possibility exists that the experimental group is in some important way different from the control group and/or from the larger population

True and false…

…selection-treatment interaction is an uncontrolled variable in research designs involving randomization

True and false…

…it is possible to know what a researcher means by the terms assigned to variables without clear operationalized descriptions

True and false…

…good designs control for many sources of invalidity, poor designs control few

True and false…

…ANCOVA is used to “correct” or adjust posttest scores for initial pretest differences

True and false…

…ANCOVA is assumes that the relationship between the independent and covariate variables is curvilinear

True and false…

…a researcher should not totally accept or reject a research design because of how it controls (or fails to control) for sources of invalidity

True and false…

…a researcher should decide which research design is most appropriate not only by the controls provided but also by the nature of the study and the setting in which it is to be conducted

True and false…

…in a static-group comparison design, each group serves as a control or comparison group for the other group(s)

True and false…

…in a counterbalanced design, the average performance of the groups on each treatment are calculated and compared

True and false…

…in a true experimental designs, participants should be randomly selected or randomly assigned

True and false…

…in the pretest-posttest control group design, if groups are essentially the same on the dependent variable at the start of a study, a t-test can be used for analysis; if not, ANCOVA is used

True and false…

…the more dissimilar the intact groups in a study are, the stronger the study is

True and false…

…when describing and symbolizing factorial designs, the control variable is placed first

True and false…

…the purpose of a factorial design is to determine whether the effects of an independent variable are generalizable across all levels or are specific to particular variables

True and false…

…factorial designs are very effective for testing research hypotheses that cannot be tested with a single-variable design

True and false…

…for all types of research, the more a study’s results are replicated, the less confidence there is in the procedures that produced those results

Fill in the blank…

…the two main ways that researchers equate groups participating in experimental research

simple random sampling

stratified random sampling

…the researcher decides what treatment(s) will constitute the independent variable and which group will get which treatment

manipulation

…the researcher’s efforts to remove the influence of any extraneous variable that might affect scores on the dependent variable

control

…the researcher’s concern with threats or factors other than the independent variable that affect the dependent variable

internal validity

…the researcher’s concern with the extent to which the study results can be generalized to groups and settings beyond those of the experiment

external validity

…a threat to validity involving the tendency for scores to more toward a average or expected score

statistical regression

…a threat to internal validity that may be overcome by testing for initial equivalence between groups

differential selection of participants

…the population from which a researcher endeavors to extract a sample

target population

…the actual population from which a researcher extracts a sample

accessible population

…the influences on the part of the experimenter over which the experimenter has no direct control but may affect study procedures

passive experimenter effects

experimenter personal-attributes effects

…the situation in which a researcher's expectation of the study affect the researcher’s behavior and the researcher outcomes

active experimenter effect

experimenter bias effect

…an external variable that effects the independent variable and intertwines with other extraneous variables such that it is difficult to determine the unique effects of each

confounding variable

…the term referring to a design that has more than one independent variable

factor(ial)

…a study to compare the achievement of two groups: one group taught in an anxiety-producing environment and one group taught in an anxiety- reducing environment

experimental

…the nonmanipulated variable in a factorial design

control variable

…a second study conducted by a different investigator, with different participants, behaviors, and settings

systematic replication

…additional studies that add confidence to the procedures that produced those results

replication

Fill in the blank……a second study involving the development of treatment

packages, composed of two or more interventions that have been found to be effective individually, designed for persons with complex behavior disorders

clinical replication

…a second study conducted on a number of participants with the same problem, location, or time

simultaneous replication

This module has focused on...This module has focused on...

experimental studies

...which test hypotheses to establish cause-and-effect relationships

The next module will focus on...The next module will focus on...

descriptive statistics

…the set of mathematical procedures for describing, synthesizing, analyzing, and interpreting quantitative data

educational research: experimental studies edu 8603 educational research richard m. jacobs, osa,...

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