chapter 11

Question 1

How to eliminate internal validity threats and increase studys power to avoid null effects?

Answer 1

Double blind, measure variables separately, put ppl in controlled environments

Question 2

Threats to internal validity (12)

Answer 2

DDOORS PITHAM

Design confounds
Selection effects
Order effects
Observer bias
Demand characteristics
Placebo effects
Threats esp relevant for one group, pretest/posttest design:
Maturation
History
Regression
Attrition
Testing
Instrumental threats
NOTE: these can be ruled out if they use a comparison group

Question 3

Obscuring factors can be sorted into 2 categories of problems

Answer 3

not enough between group difference
- Results from weak manipulations, intensive measures, ceiling or floor effects, or a design confound acting in reverse

Too much within groups variability
- Caused by measurement error, irrelevant individual diffs, situation noise
- Can be counterated by using multiple measurements, more precise measurements, within group design, larger sample, and very controlled environments

Question 4

maturation threat

Answer 4

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 5

History threat

Answer 5

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

Question 6

Regression threat

Answer 6

phenomenon in which any extreme finding is likely to be closer to its
own typical level the next time it is measured (with or
without the experimental treatment or intervention).

Question 7

Regression to the mean

Answer 7

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 of chance factors that made the finding
extreme are not present the second time.

Question 8

Attrition threat

Answer 8

In a pretest/posttest, repeated-measures, or quasi-experimental study,
a threat to internal validity that occurs when a systematic type of
participant drops out of the study before it ends.

Question 9

Testing threat

Answer 9

In a repeated-measures experiment or quasi-experiment, a kind of
order effect in which scores change over time just because
participants have taken the test more than once; includes practice
effects.

Question 10

Instrumentation threat

Answer 10

A threat to internal validity that occurs when a measuring instrument
changes over time.

Question 11

Selection history threat:

Answer 11

A threat to internal validity in which a historical or seasonal event
systematically affects only the participants in the treatment group or
only those in the comparison group, not both.

Question 12

Selection attrition threat:

Answer 12

A threat to internal validity in which participants are likely to drop
out of either the treatment group or the comparison group, not both.

Question 13

Demand characteristics

Answer 13

A cue that leads participants to guess a study’s hypotheses or goals; a threat to internal validity. Also called experimental demand.

Question 14

Ceiling effect

Answer 14

independent variable groups score almost the same on a dependent variable, such that all
scores fall at the high end of their possible distribution.

Question 15

Floor effect

Answer 15

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 their possible distribution.