chapter 10

Question 1

What are the 3 types of groups in an experiment?

Answer 1

1. Control group : no treatment condition
2. Treatment group : one or more treatment conditions
3. Placebo group : given placebos

Question 2

True or False : The effect variable precedes the cause variable.

Answer 2

False

Question 3

What is a design confound?

Answer 3

A design confound is a second variable which varies systematically with the independent variable (offers an alternative explanation).

Question 4

What is systematic variability?

Answer 4

When we have certain qualities overrepresented in one level of the variable or in one group. Any relationship that we saw between the independent and dependent variable may be confounded.

Question 5

What is unsystematic variability?

Answer 5

Personal characteristics that are evenly distributed through the groups.

Question 6

What is a selection effect?

Answer 6

A selection effect is when the participants in one level of the independent variable are systematically different than the other participant group.

Question 7

How can we avoid selection effect?

Answer 7

In using random assignment, we get an even distribution, thus avoiding selection effect. We can also use matched groups (e.g.: two participants with highest GPA will each be in separate groups, and so on).

Question 8

What is an independent-groups design (between-subjects design)?

Answer 8

Separate groups receive different levels of the independent variable.

Question 9

What is a within-groups design (within-subjects design)?

Answer 9

Every participant receives every level of the independent variable. Every single person acts as their own control.

Question 10

What types of designs are seen in an independent-groups design?

Answer 10

Posttest-only design
Pretest-posttest design

Question 11

What types of designs are seen in a within-groups design?

Answer 11

Repeated-measures design
Concurrent-measures design

Question 12

What is a repeated measures design?

Answer 12

Participants respond to a dependent variable more than once, after exposure to each level of the independent variable.

Question 13

What is a concurrent-measures design?

Answer 13

Participants are exposed to all the levels of an independent variable at roughly the same time and a single attitudinal or behavioural preference is the dependent variable.

Question 14

What are some advantages of within-groups designs?

Answer 14

Participants in the groups are equivalent because they are the same participants serving as their own control. This design requires fewer participants.

Question 15

What is an order effect? Give an example

Answer 15

In a within-groups design, order effect is a threat to internal validity in which exposure to one condition changes participant response to a later condition.
Example : tasting chocolate alone, rating it, then tasting the chocolate with someone else – tasting the chocolate twice may influence the rating.

Question 16

How can order effect be avoided? Give an example

Answer 16

We can avoid order effects by counterbalancing ; in a repeated-measures design, presenting the levels of the independent variable to participants in different sequences.
Example : In the chocolate tasting case, having one group taste the chocolate alone at first and then with someone else, and the other group doing the opposite.

Question 17

What are the two types of order effects?

Answer 17

1. Practice effect : Occurs when participants either get better (due to practice) or worse (due to fatigue) at a task.
2. Carryover effect : Contamination from one condition to the next (brushing teeth, then drinking OJ)

Question 18

What are some of the disadvantages of within-groups designs?

Answer 18

There are potential order effects ; they may not be practical or possible ; experiencing all levels of the IV changes the way participants act (i.e : a demand characteristic : they might know what the study is about and alter their behaviour)

Question 19

What is a demand characteristic (also called experimental demand)?

Answer 19

A demand characteristic is a cue that leads participants to guess a study’s hypothesis or goals, thus a threat to internal validity because they may alter their behaviour.

Question 20

What is a mixed design?

Answer 20

A mixed design is a combination of a between-subjects factor and a within-subjects factor.
Example :
IV1 : laptop vs. hand written notes (between subjects factor)
IV2 : factual vs. conceptual (within subjects factor)
this shows a 2x2 factorial design