Chpt 8: Experimental Design (PSY302)

Question 1

Def: Confounding variable

Answer 1

a variable that varies along with the IV.
Confounding occurs when the effects of the IV and an uncontrolled variable are intertwined.
It cannot be determined which variable is responsible for the observed effect on the DV.
Good experimental design requires eliminating all possible confounding variables that could result in alternative explanations

Question 2

When results can ________ be attributed to the IV, the experiment is said to have ____________ validity.

Answer 2

confidently, internal

Question 3

Explain: Posttest Only Design

Answer 3

Obtain 2 equivalent groups of participants.
Manipulate the IV
Measure the effect of the IV on the DV
Procedures used have to eliminate any potential selection diffs: the ppl selected to be in the conditions cannot be different in any systematic way.

Question 4

Def: selection diffs

Answer 4

systematic diffs between the participants assigned to each group - has to be avoided.

Question 5

Def: Pretest-posttest design

Answer 5

a pretest is given before the experimental manipulation
A pretest is usually not necessary if participants are randomly assigned & the sample is sufficiently large.
Makes it possible to ascertain that the groups were equivalent at the beginning of the experiment.

Question 6

Pros for using a Pretest-posttest design

Answer 6

The pretest enables the researcher to tell whether the experimental corpus were equivalent to begin with
Change can be incorporated into the analysis of group diffs & of individuals
The effects of attrition or mortality - the participants’ dropout factor in experiments - can be assessed.
Useful whenever there is a possibility that participants will drop out of the experiment which is most likely to occur over a long period of time.

Question 7

Cons for using a Pretest-posttest design

Answer 7

It his time-consuming & awkward to administer
It can sensitize participants to what is benign studied, tho this can be mitigated by disguising the pretest.

Question 8

Def: Solomon 4-group design

Answer 8

the experimental & control groups are studied with & without a pretest
Half the participants receive only the posttest & the other half of the participants receive only the pretest and the posttest
If there’s no impact of the pretest, the posttest scores will be the same in the 2 control groups & in the 2 experimental groups.

Question 9

It’s also possible to assess the impact of the pretest _________ with the combo of both.
If one does it this way, participants receive only the __________ and the other half receive both.

Answer 9

directly, posttest

Question 10

Def: independent groups design

Answer 10

participants are randomly assigned to the various conditions so that each participates in only a single group
Also known as between-subjects design bc comparisons are made between diff groups of participants

Question 11

Def: random-assignment

Answer 11

the decision abt which group each participant is assigned to is completely random & not controlled by the researcher.
Prevents systematic biases
Yields equivalent groups
Removes participant diffs as an explanation for results

Question 12

Def: Repeated measures design

Answer 12

all participants are in all conditions
Also called within-subjects design; comparisons are made within the same group of participants.

Question 13

Pros for using a Repeated Measures design

Answer 13

Fewer participants needed
Extremely sensitive to statistical diffs

Question 14

Cons for using a Repeated Measures Design

Answer 14

Order effect
Practice effect
Fatigue effect
Carryover effect

Question 15

Def: Order effect

Answer 15

the order of presenting the treatments affects the DV.

Question 16

Def: Practice effect

Answer 16

performance improves due to the practice gained from prev tasks

Question 17

Def: Fatigue effect

Answer 17

performance deteriorates bc of fatigue, boredom, or distraction.

Question 18

Def: Carryover effect

Answer 18

the effects of the 1st treatment carries over to influence the response to the 2nd treatment.

Question 19

Def: Counterbalancing

Answer 19

a method of controlling for order effect by either including all orders of treatment presentation or randomly determining the order for each subject

Question 20

Def: Latin square

Answer 20

a limited set of order constructed to ensure that 1) each condition appears at each ordinal position and 2) each condition precedes & follows each condition one time.

Question 21

Researchers also need to ____________ determine the time interval between presentation of treatments & possible ___________ between them.
A rest period might counteract the _________ effect
If treatments involve administration of a drug or procedures that produce emotional changes, a long time ___________ is often necessary

Answer 21

carefully, activities, fatigue, interval

Question 22

Some real-world situations are comparable to _____________ groups designs, while others more closely resemble repeated measures designs.

Answer 22

independent

Question 23

Experiments that produce relatively permanent ___________ in ppl cannot use repeated measures designs.

Answer 23

changes

Question 24

Def: matched Pairs design

Answer 24

participants are matched based on a participant variable; the matching variable will be either the DV or something that is sternly related to the DV
The members of each pair are then randomly assigned to the diff conditions of the experiment.
This ensures the groups are equivalent, which is particularly important with small sample sizes
Note that bc matching procedure can be costly & time-consuming, matched pairs is not a commonly used experimental design

Question 25

What’s the 1st step to a Matched Paris design

Answer 25

First step is to get a measure of the matching variable from each of the participants.

Question 26

Matched Pairs Design ensures that the groups are ___________ prior to into of the IV manipulation

Answer 26

equivalency