Question

A physical education teacher uses a nonequivalent pretest-posttest experimental control group design to test the effectiveness of a new exercise routine on student flexibility with four classes of tenth graders. What are the threats and justifications to internal and external validity?

Answer #1

For many true experimental designs, pretest-posttest designs are the preferred method to compare participant groups and measure the degree of change occurring as a result of treatments or interventions.

**Internal validity** refers specifically to
whether an experimental treatment/condition makes a difference or
not, and whether there is sufficient evidence to support the
claim.

**External validity** refers to the
generalizability of the treatment/condition outcomes.

T**he factors of internal validity -**

History, Maturation, Testing, Instrumentation, Statistical regression, Selection of subjects, Experimental mortality, Selection-maturation interaction,

**Factors of external validity-**

Reactive or interaction effect of testing, Interaction effects of selection biases and the experimental variable, Reactive effects of experimental arrangements, Multiple treatment interference

Define the following terms: 1. Confound 2. Internal Validity 3.
Multiple-group Time-series Design 4. Non-equivalent Control Group
Posttest Only Design 5. Non-manipulated Independent Variable 6.
Regression to the Mean 7. Single-group Posttest Only Design 8.
Single-group Pretest-posttest Design 9. Single-group Time-series
Design 10. Systematic Replication 11. Testing Effect

#1. Which of the following scenarios would be best described as
having a true experimental research design?
A
Research Question: Do a smaller proportion of graduates attend
graduation when it is held on a Sunday compared to Saturday?
Design: Randomly select 40 graduates the year it is held on a
Saturday and record how many attend graduation. Do the same thing
on a year the ceremony is held on a Sunday.
B
Research Question: Is a new vaccination effective at...

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