Chapter 11: Confounding & Obscuring Variables

Question 1

Maturation Threat

Answer 1

A threat to internal validity that occurs when an observed change in an experimental group could have emerged more or less spontaneously over time.

Question 2

History threats

Answer 2

A threat to internal validity occurs when it is unclear whether a change in the treatment group is caused by the treatment itself it by an external or historical factor that affects most members of the group.

Question 3

Regression to the mean

Answer 3

A phenomenon in which an extreme finding is likely to be closer to its own typical, or mean, level the next time it is measured because the same combination or change factors that made that finding extreme are not present the second time.

Question 4

Regression Threat

Answer 4

A threat to internal validity related to regression to the mean, a phenomenon in which any extreme finding is likely to be closer to its own typical, or mean, level the next time is is measured (with or without the experimental treatment or intervention).

Question 5

Null effect / null result

Answer 5

A finding is that an independent variable did not make a difference in the dependent variable; there is no significant covariance between the two.
Hypothetically, if there is an effect, but it presents null, it could be to:
- weak manipulations
- insensitive measures
- ceiling and floor effects
- Noise (too much unsystematic variability)

Question 6

Ceiling Effect

Answer 6

An experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the high end of their possible distribution.
- questions being two easy, everyone will get a perfect score

Question 7

Floor Effect

Answer 7

An experimental design problem in which independent variable groups score almost the same on a dependent variable, such that all scores fall at the low end of the possible distribution.
- questions are too hard, everyone will score low

Question 8

Manipulation check

Answer 8

A separate dependent variable that experimenters include in a study to make sure the manipulation worked.

Question 9

Noise/error variance / unsystematic variance

Answer 9

Unsystematic variability among the members of a group in an experiment, which might be caused by the situation noise, individuals differences, or measurement error

Question 10

Measurement Error

Answer 10

The degree to which the recorded measure for a participant on some variable differs from the true value for that participant. Measurement errors may be random, such that scores that are too high and too low cancel each other out, or they may be systematic, such that most scores are biased too high or too low.