Threats to Internal Validity I
Which type of threat to internal validity is illustrated by the following: Disruptive boys settle down as they get used to the camp setting
Maturation threat
This effect occurs when there is an event or external factor that effects the treatment group concurrently with the independent variable
History threat
What is the most common measure taken, mentioned many times throughout the chapter, to ameliorate many internal validity threats
move to a posttest only design
T or F; null effects occur always as a consequence of faulty experimental design
False, sometimes null effects occur because there is not effect of the IV on the DV
Which type of threat to internal validity is illustrated by the following: GRE verbal scores improve only because students take the same version of the test both times and therefore are more practiced at post-test
Testing Effects
Regression threat refers to what statistical concept. Define it briefly
Regression to the mean; overtime, more extreme scores will regress back to the average
What is a posttest only design
Foregoing a measure at pretest and only measuring the dependent variable at a single time after exposure to the Independent Variable
This term refers to the effect that results from not effecting the Independent Variable enough to get anything but null effects
Weak Manipulations
Which type of threat to internal validity is illustrated by the following: Coders get more lenient over time, so the same behavior is coded as less disruptive at posttest than at pretest
Instrumentation threat
This threat to internal validity occurs when participants drop out in between pretest and posttest in one group pretest/posttest designs. Particularly an issue if outliers drop out
Attrition threat
Other than moving to a posttest only design, what measures might researchers take to fix attrition threats
remove those participants scores from the data altogether
Weak manipulations, floor effects, and ceiling effects can all be helped by what?
Manipulation checks
Which type of threat to internal validity is illustrated by the following: Campers notice that the experimenter talks much more calmly to their group vs. the other group, so they change their behavior
Demand effect
Along with placebo effects and demand characteristics, this threat to internal validity can effect any study.
Observer Bias, when observers expectations influence results
Both history effects and regression effects can be buttressed against by?
Adding a comparison group
"noise" refers to what when discussing within groups variability. What is it caused by?
Noise is unsystematic variance between participants. It can be caused by situation noise, individual differences, or measurement error
Which type of threat to internal validity is illustrated by the following: Women receiving cognitive behavioral therapy improve simply because they believe it will work
Placebo effect
Define both combined threats: Selection History threat and Selection Attrition threat.
Selection history threat: When only one group of participants (either control or treatment) are effects by history threat
Selection Attrition effect: When participants in one group, not both, are likely to drop out of the study in between pretest and posttest
Mentioned in previous chapters, this study design is employed to deal with both observer bias and demand characteristics
Double-blind study
In the text, on the discussion of Precision and Power, what are the benefits of larger sample sizes
Larger sample sizes will produce narrower confidence intervals meaning more precise estimates of a population mean
Larger sample sizes also reduce the probability of chance findings.