Ch. 8: Experimental Designs: Between-Subjects Design

Question 1

two basic experimental research designs

Answer 1

within-subjects and between-subjects designs

Question 2

within-subjects design

Answer 2

the groups of scores all can be obtained from the same group of participants

Question 3

between-subjects design

Answer 3

involves obtaining each group of scores from a different group of participants

Question 4

synonym for between-subjects design

Answer 4

independent-measures experimental design

Question 5

goal of between-subjects designs

Answer 5

to determine whether differences exist between two or more treatment conditions

Question 6

independent scores

Answer 6

there is only one score for each participant

Question 7

advantages of between-subjects designs

Answer 7

• Each score is independent of other scores, so it is not influenced by factors such as practice, fatigue, or contrast effects
• Can be used for a wide variety of research questions

Question 8

disadvantages of between-subjects designs

Answer 8

• They require a relatively large number of participants
• Individual differences

Question 9

individual differences

Answer 9

personal characteristics that differ from one participant to another

Question 10

concerns about individual differences

Answer 10

• Individual differences can become confounding variables
• Individual differences can produce high variability in the scores

Question 11

Two major sources of confounding that exist in a between-subjects design

Answer 11

Individual differences
Environmental variables

Question 12

The separate groups in a between-subjects design must be

Answer 12

created equally, treated equally, composed of equivalent individuals

Question 13

created equally

Answer 13

the process used to obtain participants should be as similar as possible for all of the groups

Question 14

treated equally

Answer 14

except for the treatment conditions that are deliberately varied between groups, the groups of participants should receive the same experiences

Question 15

composed of equivalent individuals

Answer 15

the characteristics of participants in any one group should be as similar as possible to the characteristics of the participants in every other group

Question 16

three ways to limit confounding by individual differences

Answer 16

1. Random assignment (randomization)
2. Matching groups (matched assignment)
3. Holding variables constant or restricting the range of variability

Question 17

goal of random assignment

Answer 17

to ensure that all individuals have the same chance of being assigned to a group

Question 18

assumption of random assignment

Answer 18

It is reasonable to assume that characteristics such as age, IQ, and gender are also randomly distributed across groups

Question 19

restricted random assignment

Answer 19

the group assignment process is limited to ensure predetermined characteristics (such as equal size) for separate groups

Question 20

advantage of random assignment

Answer 20

it is fair and unbiased

Question 21

disadvantage of random assignment

Answer 21

it doesn’t guarantee a perfectly balanced outcome; in the long run, it will be fair, but in the short run, anything can happen by chance

Question 22

matching groups

Answer 22

involves assigning individuals to groups so that a specific participant variable is balanced, or matched across the groups

Question 23

goal of matching groups

Answer 23

to create groups that are equivalent concerning the variable matched

Question 24

three steps of matching groups

Answer 24

1. Identification of the variable(s) to be matched across groups
2. Measurement of the matching variable for each participant
3. Assignment of participants to groups using restricted random assignment ensures a balance between groups

Question 25

advantage of matching groups

Answer 25

provides a relatively easy way to ensure that specific participant variables do not become confounding

Question 26

disadvantages of matching groups

Answer 26

- The researcher must first measure the matched variable which can be tedious and costly - It can be difficult or impossible to match groups on several different variables simultaneously - Groups cannot be matched on every single variable that might differentiate participants

Question 27

advantage of holding variables constant or restricting range of variability

Answer 27

it can be an effective way to prevent the variable from confounding

Question 28

disadvantage of holding variables constant or restricting range of variability

Answer 28

it limits the external validity of the research

Question 29

recommendations for limiting confounding

Answer 29

- Random assignment provides a simple way of balancing characteristics across groups without addressing reach individual variable - When one or two specific variables can be identified as likely to influence the dependent variable, use matching or holding the variable constant

Question 30

individual differences and variability

Answer 30

- Individual differences have the potential to produce high variability in the scores - This can obscure treatment effects and undermine the likelihood of a successful study

Question 31

variance

Answer 31

a statistical value that measures the size of the differences from one score to another

Question 32

variance and patterns in the data

Answer 32

Large variances can obscure patterns in the data

Question 33

differences between treatments and variance within treatments

Answer 33

- Big differences between treatments are good because they provide evidence of differential treatment effects - Big differences within treatments are bad because the differences that exist inside the treatment condition determine the variance of the scores

Question 34

4 ways to minimize variance within treatments

Answer 34

- standardize procedures and treatment setting - limit individual differences - random assignment and matching - sample size

Question 35

standardize procedures and treatment setting

Answer 35

be sure that participants within a group are treated the same

Question 36

limit individual differences

Answer 36

this can be done by matching variables, holding variables constant, or restricting their range

Question 37

random assignment and matching

Answer 37

this has no effect on the variance within groups

Question 38

sample size

Answer 38

using a large sample size can help minimize the problems associated with high variance

Question 39

what is the best way to minimize the negative consequences of high variance?

Answer 39

to standardize treatments and minimize individual differences between participants

Question 40

two advantages of holding a variable constant or restricting its range

Answer 40

- It helps create equivalent groups, which reduces the threat of confounding variables - It helps reduce the variance within groups, which makes the treatment effects easier to see