ch6

Question 1

“The” experiment: terminology

Answer 1

Data collection method where one or more IVs are manipulated to measure the effect on the DV, and where you control for other causes

Question 2

Ways to manipulate an IV

Answer 2

• Presence vs absence (e.g. bonus vs no bonus)
• Frequency (e.g. high bonus vs low, vs no bonus)
• Type (e.g. punishment vs reward)

Question 3

Extraneous variable

Answer 3

Every possible variable that can influence the DV, other than the IV

•E.g. Store location, age, gender, culture..

Question 4

The 2 main objectives of experimental studies

Answer 4

• To draw valid conclusions about the effects of IV(s) on DV (requires internal validity)
• To make valid generalisations towards a broader group/population (requires external validity)

Question 5

Confound

Answer 5

A variable (Z) that threatens internal validity

To prevent confounds, include extraneous and control variables in the design

Question 6

Lab experiment

Answer 6

Artificial setting to have as much control as possible over the manipulations (including online experiment)

Question 7

Field experiment

Answer 7

Natural environment where manipulation is possible

• Problems with randomisation
• Problems to exclude external influences

Question 8

Threats to internal validity: History effect

Answer 8

Events/factors outside the experiment have an impact on the DV during the experiment

Question 9

Threats to internal validity: Maturation effect

Answer 9

Biological/physiological changes over time

Question 10

Threats to internal validity: Testing effect

Answer 10

Prior testing affects the DV

Question 11

Threats to internal validity: Instrumentation effect

Answer 11

The observed effect is due to a change in measurement

Question 12

Threats to internal validity: Selection bias effect

Answer 12

Incorrect selection of respondents (experimental and/or control group)

Question 13

Threats to internal validity: Mortality effect

Answer 13

Drop out of respondents during experiment

Question 14

Threats to internal validity: Statistical regression effects

Answer 14

Extreme scores in the beginning and less extreme in the end, this is also called: regression to the mean

Question 15

Illustration field study: One group pretest post test

Answer 15

e.g. you give all employees in a company a bonus, and you compare work motivation before bonus (t-1) with motivation after bonus (t)

O1 X O2
“Within participants”

Problems
•Possible changes in the company (e.g. MT) -> history effect
•Employees got more mature -> maturation effect
•Filling in the same questionnaire twice (01 and 02 can lead to) -> testing effects

Question 16

Illustration field study: Static design

Answer 16

e.g. you split the group of employees within a company in 2, give one group a bonus and the other group no bonus. You compare work motivation of the treatment group with work motivation of the control group.

G1: X 01
G2: 02
“Between participants”

Problems:
•Possible (demographic) differences between groups might explain the effects -> selection bias effect
•Participants in the control group may be frustrated and leave the company -> mortality effect

Question 17

Increasing internal validity: controlling for extraneous variables

Answer 17

• Randomization: random allocation of participants to different conditions (selection bias, but also instrumentation, history, mortality) *difficult to control in the field
• Design control
  • Control group: include group that does NOT receive the treatment (history, and maturation, but also instrumentation and statistical regression)
  • Extra groups: groups without pre-test, but with an experimental manipulation (to exclude the effects of pre-testing) (testing)

•Statistical control: measure extraneous variables, and include theses in the statistical analysis (covariance analysis) (history and selection bias)

Question 18

Illustration lab study: True lab experiment

Answer 18

E.g. You randomly allocate participants to conditions, ask them to work on a task, and make sure that the only thing that is different between groups is the fact that you give a bonus to group 1 and no bonus to group 2.

G1: R X 01
G2: R 02
“Between participants”

Problems:
•External validity

•In many cases it is wise to start research with an internally valid lab experiment and let it be followed by an externally valid real life field experiment