Chapter 10 Simple Experiments

Question 1

basic definition of an experiment

Answer 1

a study where at least 1 variable is manipulated and others are measured

Question 2

control variables are also known as what?

Answer 2

extraneous variables or confounds

Question 3

extraneous variable vs confound vs third variable

Answer 3

extraneous: variables that are not the focus of the research but may impact the variables being studied
confound: extraneous variable in EXPERIMENTAL RESEARCH that provides an alternative explanation
third variable: extraneous variable in CORRELATIONAL RESEARCH that provides an alternative explanation

Question 4

how are confounds and third variables related to the variables of interest in their respective studies?

Answer 4

confounds vary systematically with the IV and MAY impact the DV
third variables are associated with both IV and DV (could be a spurious correlation)

Question 5

what does “treatment” refer to in experiments?

Answer 5

the manipulated condition that researchers are most interested in; not necessarily medicine

Question 6

IV levels vary. what are 3 types of groups seen in experimental studies?

Answer 6

treatment groups, comparison groups and control groups

Question 7

comparison group

Answer 7

level of IV that differs from the treatment in a meaningful way

Question 8

control group

Answer 8

neutral/no treatment condition

Question 9

main type of control group

Answer 9

placebo group: group receives an inert treatment

Question 10

true or false: every experiment needs a control condition

Answer 10

false

Question 11

true or false: every experiment needs a comparison group

Answer 11

true

Question 12

adding a control condition to an experiment may help tell what?

Answer 12

the direction of effects

Question 13

confounds threaten which validity?

Answer 13

internal

Question 14

what may be the cause of design confounds?

Answer 14

the IV operationalization/aspects of experimental procedure

Question 15

systematic variability

Answer 15

the levels of a third variable vary alongside IV variation/dif levels of the IV

Question 16

unsystematic variability

Answer 16

the levels of a variable vary independently of experimental groups

Question 17

selection effects

Answer 17

characteristics of participants in one level of the IV are systematically different than that of participants in the other levels of the IV

Question 18

2 ways to avoid selection effects

Answer 18

random assignment & matched groups

Question 19

2 types of confounds

Answer 19

design confounds and selection effects

Question 20

blocked random assignment

Answer 20

ensuring equal numbers of people are in each condition

Question 21

goal of matched groups

Answer 21

ensuring groups are as equal as possible on important variables

Question 22

3 steps to attaining matched groups

Answer 22

1. measure an important participant variable
2. put people with comparable scores in pairs
3. within each pair, randomly assign 1 person to each condition

Question 23

how is control of the IV obtained in experiments?

Answer 23

manipulation of the IV

Question 24

how is control of extraneous variables and confounds obtained?

Answer 24

random assignment & holding variables constant on purpose

Question 25

control over the IV can establish what?

Answer 25

temporal precedence

Question 26

what 3 things are controlled in good experiments?

Answer 26

IV, confounds and extraneous variables

Question 27

2 main points of independent-groups designs

Answer 27

-different groups of participants are on different levels of the IV -participants' characteristics are not matched

Question 28

independent groups designs are AKA what?

Answer 28

between-groups design, betweem-subjects design

Question 29

2 types of independent groups designs

Answer 29

posttest only pretest/posttest

Question 30

posttest-only design

Answer 30

participants are randomly assigned to IV groups and are tested on the DV ONLY ONCE

Question 31

pretest/posttest design

Answer 31

participants are randomly assigned to IV groups and are tested on the DV TWICE (once before and once after IV exposure)

Question 32

goals of pretest/posttest

Answer 32

show that RA made groups equal track change in the DV over time

Question 33

why is it sometimes problematic to use a pretest/posttest design?

Answer 33

the pretest may change participants behavior, at risk for bias

Question 34

main point of within groups design

Answer 34

each participant is exposed to all levels of the IV

Question 35

2 types of within groups designs

Answer 35

repeated-measures concurrent-measures

Question 36

repeated-measures design

Answer 36

participants are measured on a DV more than once, after exposure to each level of the IV

Question 37

concurrent-measures design

Answer 37

participants are exposed to all levels of the IV at roughly the same time, and a preference is the measured DV

Question 38

advantages of within-groups design

Answer 38

1. participants are their own control group 2. very powerful in the sense that the study can show a statistically significant result when an IV truly has an effect on the DV 3. fewer participants required

Question 39

which design typically has more power?

Answer 39

within groups

Question 40

how can order effects threaten internal validity of w/in groups designs?

Answer 40

the order in which IV levels are presented creates a confound because one IV level can affect participants' reactions to later IV levels

Question 41

3 main types of order effects

Answer 41

practice effects, fatigue effects and carryover effects

Question 42

practice effects

Answer 42

performance improves in later conditions only because participants were able to practice on the DV in earlier conditions (not because of the IV)

Question 43

fatigue effects

Answer 43

tiredness and boredom can lead to worse performance in later conditions (as time goes on)

Question 44

carryover effects

Answer 44

contamination carries over from one condition to the next/ effects of one condition carryover to other conditions

Question 45

counterbalancing

Answer 45

different participants are exposed to different orders of the conditions

Question 46

goal of counterbalancing

Answer 46

to control for order effects

Question 47

full vs partial counterbalancing

Answer 47

full: all possible sequences of conditions are presented partial: only some possible sequences are presented

Question 48

when is partial counterbalancing typically used more often?

Answer 48

when there is a large number of conditions (by 4 conditions theres already 24 sequences, 5 conditions 120 sequences, etc)

Question 49

what is a Latin square generator?

Answer 49

used for partial counterbalancing; it ensures each condition appears once at each serial position in the sequence and that each condition follows and precedes each other condition once

Question 50

disadvantages of w/in groups designs

Answer 50

1. order effects 2. might not be practical or possible 3. demand characteristics

Question 51

demand characteristics

Answer 51

cues that lead participants to guess the experiment's hypothesis

Question 52

construct validity in experiments

Answer 52

how well were the DVs measured and how well were the IVs manipulated

Question 53

manipulation check

Answer 53

an extra dependent measure to test the effectiveness of manipulation

Question 54

pilot study

Answer 54

very simple study to test the effectiveness of manipulations of the IV

Question 55

external validity in experiments

Answer 55

can the causal claim be GENERALIZED to other people/situations?

Question 56

there is said to be a trade off b/w which 2 validities? why?

Answer 56

internal and external; bc experimental control may require artificial situations in the lab

Question 57

internal validity in experiments

Answer 57

are there design confounds, selection effects or order effects?

Question 58

statistical validity for experiments

Answer 58

how large is the effect?

Question 59

Cohen's d

Answer 59

the standardized difference b/w 2 means

Question 60

more thorough explanation of Cohen's d

Answer 60

consider the mean difference b/w groups and the spread of scores within each group

Question 61

the larger d is, the larger the _______ is

Answer 61

effect

Question 62

Cohen's d cutoffs

Answer 62

0.2- small effect size 0.5- moderate 0.8- large