Exam 2

Question 1

for a study to be an experiment, it has to have…

Answer 1

• at least one manipulated variable
• at least one measured variable

Question 2

control variable

Answer 2

a variable that an experimenter holds constant on purpose (besides the independent variables)
- not really variables because they do not vary

Question 3

why experiments support causal claims through the 3 criteria

Answer 3

• establish covariance: changes in the independent variables are related to the changes in the dependent variable
• establish temporal precedence: The causal variable should come before the outcome variable
• establish internal validity: There are no other likely explanations for the relationship observed

Question 4

placebo (control) groups

Answer 4

a group that is exposed to an inert treatment; comparison group may not need to be a control group (i.e., no treatment)

Question 5

confounds

Answer 5

an unmeasured variable that influences both the supposed cause and the supposed effect

Question 6

design confounds

Answer 6

an accidental second variable varies systematically along with the intended independent variable

Question 7

selection confounds (selection effects)

Answer 7

when the kinds of participants in one level of the independent variable are systematically different from those in the other
- avoid selection effects with random assignment
- avoiding selection effects with matched groups

Question 8

types of experimental design

Answer 8

• independent-groups designs (between-sujects)
• within-subjects designs
• pottest-only designs
• pretest/posttest designs

Question 9

independent-groups designs (between-subjects)

Answer 9

Separate groups of participants are placed into different levels of the independent variable
- Ex. an experiment exploring how different amounts of sleep affect people’s reaction times → level 1: 3 hours of sleep, level 2: 8 hours of sleep

Question 10

within-subjects designs

Answer 10

• Each person is presented with all levels of the independent variable
• One set of participants are tested more than once, and their scores are compared
• Ex. an experiment exploring how different amounts of sleep affect people’s reaction times → all groups do day 1 with 3 hours of sleep and day 2 with 8 hours of sleep

Question 11

posttest-only designs

Answer 11

Participants are randomly assigned to independent variable groups and are tested on the dependent variable once

Question 12

pretest/posttest designs

Answer 12

Participants are randomly assigned to at least two difference groups and are tested on the key dependent variable twice— once before and once after exposure to the independent variable

Question 13

problems using pretest/posttest design

Answer 13

threat to internal validity
- Taking the pretest affects how participants do the posttest → testing threat
- Participants may get tired from a long study with a pretest and posttest

Question 14

repeated-measures design

Answer 14

participants are measured on a dependent variable more than once, after exposure to each level of the independent variable

Question 15

concurrent-measures design

Answer 15

participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable

Question 16

advantages of within-groups design

Answer 16

• Participants in your groups are equivalent because they are the same participants and serve as their own controls
• Gives researchers more power to notice difference between conditions because there is less extraneous error in the measurement
• Requires fewer participants

Question 17

disadvantages of within-groups design

Answer 17

• potential for order effects
• carryover effects
• might not be practical or possible
• experiencing all levels of the IV changes the way participants act –> demand characteristics

Question 18

demand characteristics

Answer 18

subtle cues or aspects of an experiment that might unintentionally signal to participants what the study is about, leading them to change their behavior to fit that perceived expectation

Question 19

order effects

Answer 19

When the sequence in which stimuli are presented to participants influences their responses; order of conditions can affect the results

Question 20

carryover effects

Answer 20

• practice effect –> participants perform better during later treatment conditions because they’ve had time to practice and improve
• Fatigue effect → participants perform worse during later treatment conditions because they’re tired or fatigued

Question 21

avoiding order effects

Answer 21

• full counterbalancing
• partial counterbalancing