Chapter 11

Question 1

One-group, pretest/posttest design

Answer 1

One group measured on pretest, exposed to treatment, change and measures them on posttest. No comparison group-bad design!

Question 2

Maturation threat

Answer 2

Change in behaviour that emerges more or less spontaneously over time.

Prevented by comparison group.

Question 3

History threats

Answer 3

Historical or external factor that systematically affects most members of treatment group at same time as treatment itself. Must affect most ppl in group in same direction (systematically) not just a few ppl (unsystematically).
Prevented by comparison group.

Question 4

Regression threat

Answer 4

(Regression to mean)

When group average (mean) is unusually extreme at time 1, next time at time 2 it’s less extreme-closer to average performance.

Comparison groups along with inspection of pattern of results-if comparison group and experimental group are equally extreme at pretest, researchers can account for regression effects.

Question 5

Attrition threat

Answer 5

When pretest and posttest are administered on separate days and some ppl are not available on second day.

Problem for internal validity when attrition is systematic (when only an extreme participant drops out). Prevent by taking out the person’s results in pre and posttest. Internal validity issue if their score is extreme.

Question 6

Testing threat

Answer 6

Specific kind of order threat, refers to change in participants as result of taking a test (dependent measure) more than once. (Improved score, fatigued, bored-which could lead to worse scores)
Prevention-no pretest or different pre/posttests.

Question 7

Instrumentation threat

Answer 7

When a measuring instrument changes over time. (Observers become more lenient or strict)

Different tests used pre/posttest but not equivalent.

Prevention-posttest only, pre/posttest equivalent, retrain coders during experiment. Counterbalance version A at pretest and version B at posttest.

Question 8

Difference between Instrumentation vs testing threats

Answer 8

Measuring instrument changed from Time 1 to Time 2. Testing threat means participants changed from pre-posttest.

Question 9

Selection-history threat

Answer 9

Outside event or factor affects only those at one level of independent variable.

Question 10

Selection-attrition threat

Answer 10

Only one of the experimental groups experiences attrition.

Question 11

Observer bias

Answer 11

When researchers expectations influence their interpretation of the results.

Question 12

Observer bias threatens two types of Validity;

Answer 12

Internal and construct
(Internal: Alternative explanation exists for results)

(Construct: depression ratings given by the researcher do not represent true levels of depression)

Question 13

Demand characteristics

Answer 13

When participants guess what the study is about and change their behaviour in the expected direction.

Question 14

How do you avoid observer bias and demand characteristics?

Answer 14

Double-blind study best.

Masked/blind design (participants know which group they are in but observer doesn’t.

Question 15

Placebo effect

Answer 15

When ppl receive a treatment and really improve-but only because the recipients believe they are receiving a valid treatment.

Question 16

Double-blind placebo control study

Answer 16

Neither the ppl treating the patients, nor the patients know whether they have the placebo or real group.

Question 17

Null Effect;

Between-Groups Difference and how to fix them:

Answer 17

• Weak manipulations
• insensitive measures
• ceiling and floor effect

Prevention-was the dep/indep variable operationalized? Conduct manipulation check.