Descriptive Methods◦ Observation◦ Survey Research

Experimental Methods◦ Independent Groups Designs◦ Repeated Measures Designs◦ Complex Designs

Applied Research◦ Single-Case Designs and Small-n Research

◦ Quasi-Experimental Designs and Program Evaluation

OVERVIEW

WHY RESEARCHERS USE REPEATED MEASURES DESIGNS

THE ROLE OF PRACTICE EFFECTS IN REPEATED MEASURES

DESIGNS

◦ Defining Practice Effects

◦ Balancing Practice Effects in the Complete Design

◦ Balancing Practice Effects in the Incomplete Design

DATA ANALYSIS OF REPEATED MEASURES DESIGNS

◦ Describing the Results

◦ Confirming What the Results Reveal

THE PROBLEM OF DIFFERENTIAL TRANSFER

Repeated Measure Designs

Repeated Measure Designs◦ Within-subjects designs

Subjects are repeatedly tested Each subject in all conditions Subjects as their own controls practice and fatigue effects

◦ Improvement with practice◦ Worse with fatigue/reduced motivation

No elimination but balancing◦ Averaged across the conditions

Conduct experiment with few participants

◦ Special populations (individuals with brain injuries)

Conduct experiment more efficiently

Increase sensitivity

◦ Ability to detect the effect

◦ Minimize error variation

Study changes in behavior over time

Same individuals in each condition:◦ No confounding on individual differences variables

Practice effects: Change because of repeated testing (not because of the independent variable)

Practice effects = threat to internal validity ◦ If different conditions are presented in the same

order to all participants Two types of RMD (complete and incomplete)

◦ Differ in the ways to control for practice effects.

Block randomization◦ Random order of all condition on each presentation◦ Blocks = No of administrations of each condition (Tr/Cd)◦ Blocks Size = Number of conditions◦ Balancing = Avg presentation of each condition shall be

equal ◦ Avg Pc = Σ (cd number) / Blocks

ABBA counterbalancing◦ Random sequence followed by opposite sequence◦ Suitable for small number of conditions and trials◦ Balancing = 2 trials

Non-linear practice effects or Anticipation effects◦ Block randomization >> ABBA

Balanced across subjects Each condition in each ordinal position

◦ Orders = N! ◦ N=Conditions◦ Participants = Any Multiple of all Possible Orders

<=4 conditions : Use all possible orders Random Assignment Methods for orders selection

◦ Latin Square and Random starting order with rotation

◦ Orders = Any Multiple of Conditions

Latin Square

◦ each condition at each ordinal positions once

◦ each condition precedes and follows each other condition

exactly once

Random starting order with rotation

◦ Begin with a random order

◦ Rotate sequence systematically

Errors and outliers (data scanning)

A summary score (e.g., mean, median)

◦ Each participant (incomplete design)

◦ Each participant in each conditions (complete design)

Descriptive statistics

◦ Performance across all participants

◦ For each condition of IV

Probability testing Same as in random group design

◦ Null hypothesis testing◦ Confidence interval

Error variation◦ More sensitive◦ Not cause of individual differences◦ Difference in ways the conditions effect the

results

Persistence of effects of one condition Influence performance in subsequent

conditions Common with instructional variables

◦ Threat to internal validity of RMD Identification of DT

◦ Same variables in RMD and RGD Use RGD