chapter 9

Question 1

experimental research (descriptive vs correlational)

Answer 1

Descriptive studies allow us to describe how people think, feel, and behave

Correlational studies allow us to see relations between variables

But neither of these approaches allows us to know about the causes of behavior !!!

An experimental design answer the question why
- Whether or not one variable may be causing another variable

Question 2

Properties of a Well-Designed Experiment

Answer 2

the researcher must:
- manipulation
- random assignment
- control

Question 3

manipulation

Answer 3

vary at least one IV to assess its effects on participants’ responses

Question 4

random assignment

Answer 4

have the power to assign participants to the various experimental conditions in a way that assures their initial equivalence

Question 5

control

Answer 5

ability to control all other potential variables (i.e., extraneous variables) that may influence participants’ responses

Question 6

independent variable

Answer 6

In an experiment, the researcher manipulates one or more independent variables

An independent variable must have two or more levels

Question 7

levels

Answer 7

the different values of the independent variable
(Often referred to as conditions)

These levels can be:
Quantitative (ex: coffee dosages in the forms of 100 mg, 200mg, 300mg, 400mg)
Qualitative (ex: coffee vs decaf)

Question 8

Types of Independent Variables

Answer 8

environmental manipulations

instructional manipulations

invasive manipulations

Question 9

confederates

Answer 9

accomplices of the researcher who pose as other participants or as uninvolved bystanders (sometimes used to manipulate features of the participants’ social environment)

Question 10

environmental manipulation

Answer 10

modifications of the participant’s physical or social environment
- Change the volume, color, temperature, etc
- Use of confederates
- Ash conformity experiments

Question 11

instructional manipulations

Answer 11

vary the independent variable through the verbal instructions that participants receive
- Change the word, guidelines, framing
- Dweck mindset experiments

Question 12

invasive manipulation

Answer 12

create physical changes in the participant’s body through surgery or the administration of drugs
- Drug effectiveness studies
- Pepsi challenge

Question 13

experimental group

Answer 13

participants in an experiment who receive a nonzero level of the independent variable

Question 14

control group

Answer 14

participants in an experiment who receive a zero level of the independent variable (or the absence of the variable of interest)

Question 15

assessing the impact of the independent variable

Answer 15

Many studies fail because the independent variable is not manipulated successfully

pilot test
manipulation checks

Question 16

pilot test

Answer 16

a preliminary study that examines the usefulness of manipulations or measures that later will be used in an experiment

Question 17

manipulation checks

Answer 17

questions designed to determine whether the independent variables was manipulated successfully

Question 18

subject variables

Answer 18

a personal characteristic of research participants, such as age, gender, self-esteem, weight, or extraversion

Although they are sometimes called “independent variables,” subject variables are not true independent variables because they are not manipulated by the researcher

Question 19

dependent variables

Answer 19

the response being measured in a study, typically a measure of participants’ thoughts, feelings, behavior, or physiological reactions

Most experiments have several dependent variables

Question 20

Assigning participants to conditions

Answer 20

between participants (between-subjects) designs
- simple random assignment
- matched random assignment

within participants designs
- repeated measures designs

Question 21

simple random assignment

Answer 21

participants are placed in conditions in such a way that every participant has an equal probability of being in any experimental condition

By using random assignment, the researcher can be confident that the groups are roughly equivalent at the beginning of the study

Question 22

matched random assignment

Answer 22

research obtains participants’ scores on a measure known to be relevant to the outcome of the experiment

If there is a known variable that affects the dependent variable then matched random assignment is a better option

Participants are first matched (or paired) and then participants within each set are assigned randomly to conditions

Matched random assignment helps to ensure that the groups will be similar along some specific dimension, such as age, gender, or motivation

Question 23

within subjects design

Answer 23

aka Repeated measures design
an experimental design in which each participant serves in all conditions of the experiment

Repeated measures eliminate the need for random assignment because every participant is tested at every level of the independent variable

Question 24

Advantages of Repeated/Within-Subjects Designs

Answer 24

Control – more control than between-subjects designs because every participant is in every condition so we have more power to detect effects of the independent variable

Sample – fewer participants which give the researcher more power to detect a potential IV effect

Question 25

Main Disadvantage of Within-Subjects Designs

Answer 25

order effects - practice effects - fatigue - sensitization - carryover effects

Question 26

order effects

Answer 26

occur when the effects of a particular experimental condition are contaminated by its order in the sequence of experimental conditions in which participants are tested

Question 27

practice effects

Answer 27

participants’ responses on the dependent variable are affected by the fact that they have completed the dependent variable many times

Question 28

fatigue

Answer 28

participants become tired or bored as the experiment progresses

Question 29

sensitization

Answer 29

participants gradually become suspicious of the hypothesis as the experiment progresses

Question 30

carryover effects

Answer 30

effects of one treatment condition are still present when the participant is tested in another condition

Question 31

To guard against the possibility of order effects

Answer 31

counterbalancing latin square design

Question 32

counterbalancing

Answer 32

presenting the levels of the independent variables in different orders to different participants

Question 33

latin square design

Answer 33

each condition appears once at each ordinal position and each condition precedes and follows every other condition once

Question 34

systematic variance equation

Answer 34

Total variance = systematic variance + error variance (or unsystematic variance) Total variance = (treatment variance + confound variance) + confound variance

Question 35

We now label these constructs in experimental design terms:

Answer 35

Systematic variance – between groups variance Error variance – within group variance

Question 36

systematic variance

Answer 36

part of the total variance in participants’ responses that reflects differences among the experimental groups, and nothing more - Aka between-groups variance - If the IV has an effect on DV, we should see systematic differences between experimental conditions

Question 37

There are two sources of systematic variance (between-group variance):

Answer 37

treatment variance (primary variance) and confound variance (secondary variance)

Question 38

treatment (primary variance)

Answer 38

the portion of the systematic variance that is due to the independent variance The goal is to maximize treatment variance

Question 39

confound variance (secondary variance)

Answer 39

the portion of the systematic variance that is due to extraneous variables that differ systematically between the experimental groups **Confounding variables only affect one of the experimental groups at a time** The goal is to minimize confound variance

Question 40

confounding

Answer 40

if something other than the independent variable differs in some systematic way

Question 41

error variance

Answer 41

aka within groups variance the proportion of the total variance in participants’ responses that remains unaccounted for after systematic variance due to the independent variable is removed The goal of a researcher is to design a study that would maximize systematic variance and minimize error variance

Question 42

what is important to remember with error and confound variance

Answer 42

Error variance is unrelated to the IVs Confound variance is related to the IVs

Question 43

sources of error variance

Answer 43

individual differences transient states environmental factors differential treatment measurement error

Question 44

individual differences

Answer 44

pre-existing differences between people; this is the most common source of error variance

Question 45

transient states

Answer 45

at the time of the experiment, participants differ in how they feel (e.g., mood, health, fatigue, interest)

Question 46

environmental factors

Answer 46

differences in the environment in which the study is conducted (e.g., noise, time of day, temperature)

Question 47

differential treatment

Answer 47

despite their best efforts, experimenters do not always treat all participants exactly the same

Question 48

measurement error

Answer 48

unreliable measures increase error variance

Question 49

tips for minimizing error variance

Answer 49

- Use a homogeneous sample - Aside from differences in the independent variable, treat all participants precisely the same at all timeless - Hold all laboratory conditions (heat, lighting, noise, and so on) constant - Standardize all research procedures - Automate the experiment as much as possible - Use only reliable measurement procedures

Question 50

external validity

Answer 50

the degree to which the results obtained in one study can be replicated or generalized to - Other populations - Other research settings (e.g., lab vs. field studies)

Question 51

internal validity

Answer 51

the degree to which a researcher draws accurate conclusions about the effects of the independent variable on a dependent variable To have high internal validity, researchers must eliminate all potential confounds

Question 52

threats to internal validity

Answer 52

biased assignment pre-existing groups differential attrition pretest sensitization history effects maturation miscellaneous design confounds

Question 53

biased assignment

Answer 53

occurs when participants are assigned to conditions in a nonrandom manner

Question 54

pre-existing group differences

Answer 54

effects are due to initially nonequivalent groups rather than to the IV; this can occur when random assignment fails

Question 55

differential attrition

Answer 55

participants drop out of experimental conditions at different rates, making the experimental groups no longer equivalent

Question 56

pretest sensitization

Answer 56

completing a pretest leads participants to react differently to the independent variable than they would have reacted had they not been pretested

Question 57

history effects

Answer 57

extraneous events occurring outside of the research setting have an effect on participants’ responses

Question 58

maturation

Answer 58

changes in participants’ responses between pretest and posttest are due to the passage of time rather than the independent variable (e.g., aging, fatigue, hunger)

Question 58

miscellaneous design confounds

Answer 58

something other than the independent variable differs systematically between the experimental conditions

Question 58

Expectations can ruin a study!

Answer 58

experimenter expectancy effect demand characteristics double blind procedures

Question 59

experimenter expectancy effect

Answer 59

occurs when a researcher’s expectations about the outcome of a study influences participants’ reactions

Question 60

demand characteristics

Answer 60

occur when aspects of a study indicate to participants how they should respond. Participants can change their behavior not due to the IV but due to the experimenter expectations.

Question 61

double blind procedure

Answer 61

to avoid expectations neither the participants nor the experimenter who interacts with them know which condition the participant is in

Question 62

placebo effect

Answer 62

a physiological or psychological change that occurs as a result of the belief that an effect will occur

Question 63

placebo control group

Answer 63

administration an ineffective treatment may be used in which some participants are administered an ineffective treatment (placebo). If there is a difference between the true control group and the placebo control group, we know that a placebo effect is present

Question 64

The Experimenter’s Dilemma

Answer 64

The Trade-Off Between Internal and External Validity The more tightly controlled an experiment, the stronger its internal validity (and the more accurate conclusions one can draw about the effects of the independent variable). However, a high degree of experimental control makes the experiment more unique and less like other settings, thereby lowering external validity.