Chapter 7 Flashcards Preview

Research Methods 6114 > Chapter 7 > Flashcards

Flashcards in Chapter 7 Deck (19):

Experimental Variable

-manipulated or varied  by researcher

- is ALWAYS an independent variable



random assignment






Experimental Variable (independent)



Outcome variable (dependent)


experiemental variables

levels of experimental treatment


General Criteria for a well Designed Experiment

Essentially the characteristics that make for a good research design also apply to the design of an experiment.

1. Adequate experimental control
2. Lack of artificiality (i.e., meaningful application)
3. Has a comparison group
4. Adequate data to allow for statistical precision
5. Uncontaminated data
6. No confounding variables
7. Representativeness
8. Parsimony – mindful of number of variables explored


Construct Validity

Applies to the operational definitions of variables in experiment (construct); concerns that they could be construed for some other construct.


The extent to which a test measures one or more dimensions of a theory or trait.


Statistic Conclusion Validity

Applies to the statistical analysis and whether or not there exists a statistically significant difference between the experiment and control group.



Threats to Internal Validity

1. History - fire drill so missed class
2. Maturation - 
3.Testing (memory) - remembers questions from last test
4.Instrumentation - same post test given, one doesnt follow directions
5. Statistical Regression
7.Mortality* - dropping out
8. Selection-maturation interaction- JHS Students fatigue, HS Student do not during test


Threats to External Validity 


1. Interaction effect on testing - pretest effects

2. Interaction effects of selection biases and the experimental treatment - an effect of some selection factor of intact groups interacting with the experimental treatment that would not be the case if the groups were formed randomly

3.Reactive effects of experimental arrangements- effect due to artificial test setting

4.Multiple-treatment interference - potential carryover effect of treatments, results cannot be generalized to single treatment.


Threats to Construct Validity

1. Inadequate preoperational explication of constructs*
2. Mono-operational bias
3. Mono-method bias
4. Hypothesis-guessing within experimental conditions*
5. Confounding constructs and levels of constructs

* All within researchers control


Threats to Statistical Conclusion Validity

1. Low statistical power - using sample size that is too small to detect differences
2. Violated assumptions of statistical test 
3. Fishing and the error rate problem-capitalizing on chance findings
4. Reliability of measures - using technically inadequate measures


Post-test only control group

contains as many groups as there are experimental treatments, plus a control group

Subjects are only measured after the experimental treatments have been applied

R G1 X1 O1

R G2 X2 O2

R G3 X4 O3

R G4 X4 O4

R G5 --   O5


Pretest - posttest control group design

contains as many groups as there are experimental treatments. plus a control group

Subject are measured before and after recieving the experiemental treatments


R G1 O1 X1 O2

R G2 O3 X2 O4

R G3 O5 X3 O6

R G4 O7 --  O8


Solomon Four-Group Design

tests on the effects of pretesting

is a combination of the posttest-only control group design and the pretest-posttest control group design

four groups included only on experiment used


R G1 O1 X O2

R G2 03  -- O4

R G3  --   X O5

R G4  --   -- O6




Factorial Design

involves two or more independent variables

R G1 X1 Y1 O1

R G2 X1 Y2 O2

R G2 X2 Y1 O3

R G3 X2 Y2 04


Repeated Measures

the same subject is measured more than once on the dependent variable


R G1 X O1-O2-O3

R G2 -- O4-O5-O6