experimental design

Question 1

what is an independent variable?

Answer 1

variable which the experimenter systematically varies or manipulates

Question 2

what is a dependent variable?

Answer 2

the outcome variable as it is the variable upon which the experimenter is interested in observing effects

Question 3

what are the 3 types of independent variable?

Answer 3

situational 
task variable (different tasks)
instructional variable (given instructions or none)

Question 4

what are extraneous variables?

Answer 4

nuisance variables which may influence behaviour under investigation

but if not controlled may confound the results

Question 5

what is a confounding variable?

Answer 5

vary systematically with the IV and may effect the DV to provide alternative results

Question 6

what to do when deciding how to measure the DV in an experiment?

Answer 6

refer to previous studies

run a pilot study to make sure the task (DV) is of moderate difficulty and that the ceiling effect (too easy) and floor effect (too hard) do not disguise the differences between participants

Question 7

what should you do if the DV is too unethical to perform?

Answer 7

have a relevance-sensitivity trade off

e.g using a simulator instead of an actual car when measuring effects of alcohol on drivers

Question 8

what is a quasi-experiment?

Answer 8

IVs are comparing existing groups where differences already occur rather than manipulating the IV to make the differences occur

so the ppts are self-selected

Question 9

what conclusions can/can’t be drawn from quasi-experiments?

Answer 9

CAN
group performed differently on the DV

CAN’T
control extraneous variables
make causal inferences
say that the IV is a cause of a DV

Question 10

what conclusions can be drawn from experimental studies?

Answer 10

extraneous variables can be cotrolled for
causal inference can be made
can conclude that changes in IV cause changes in DV

Question 11

what is experimental design?

Answer 11

both the process of constructing experiments and the resulting structure of the experiments

Question 12

what is external valdity?

Answer 12

the extent to which the research findings can be generalised to other situations

Question 13

what is operationalisation?

Answer 13

the process of deciding how to manipulate and / or measure the independent variable and measure the dependent variable

Question 14

what is between-subjects manipulation?

Answer 14

systematic change to an IV where different ppts are exposed to different levels of the variable by the experimenter

Question 15

what is a manipulation check?

Answer 15

a dependent measure that checks the manipulation of the independent variable has been successful

Question 16

what is within-subjects manipulation?

Answer 16

systematic change to an IV where the same ppts are exposed to different levels of that variable by an experimenter

Question 17

what is relevance-sensitivity trade off?

Answer 17

the more relevant the DV is to the issue that the researcher is interested in, the less sensitive it may be to variation in the IV

Question 18

what are demand characteristics?

Answer 18

cues that convey an experimental hypothesis to ppts

Question 19

what is statistical conlusion validity?

Answer 19

using appropriate statistical procedures

Question 20

what is construct vakidity?

Answer 20

operational definitions of the IVs and DVs fit the purpose of the study

Question 21

ecological validity

Answer 21

generalising to other environments

Question 22

temporal validity

Answer 22

generalising to otheirtimes

Question 23

what are the 2 types of external validity?

Answer 23

temporal

ecological

Question 24

what is naive empiricism?

Answer 24

when experimental findings aren’t used to validate a theory and are instead dircetly applied to the real world

Question 25

threats to internal validity

Answer 25

``` history effects maturation effects regression to the mean testing effect instrumentation effect selection effects mortality ```

Question 26

what are history effects?

Answer 26

event occurs between pretest and posttest and affects the study outcome

Question 27

what are maturation effects?

Answer 27

ppts naturally change between pretest and posttest

Question 28

what is regression from the mean?

Answer 28

ppts may perform extremely poorly in the pretest and likely to improve for posttest independently

Question 29

what is the testing effect?

Answer 29

ppts perform better at posttest because they had practice | ppts perform worse at posttest because they got tired

Question 30

what is the instrumentation effect?

Answer 30

performance differs between pre and posttests because different measures are used

Question 31

how to control for most threats to internal validity?

Answer 31

use a control group

Question 32

what are selection effects?

Answer 32

happen when random assignment fails e.g ppts in different conditions aren't equivalent

Question 33

what is mortality?

Answer 33

ppts with certain characteristics drop out of the study e.g angry or shy

Question 34

what is between-subject design

Answer 34

i.e independent measures | ppts selected to one condition only and the different conditions are compared

Question 35

what is within-subjects design?

Answer 35

ppts take part in two or more conditions and a comparision is made within the group i.e repeated masures

Question 36

when is a between-subject design used?

Answer 36

when experience gained from one condition makes it impossible to participate in another

Question 37

advantage of a between-subject design?

Answer 37

each ppts is fresh and naive to hypothesis

Question 38

disadvantages of between-subject design? x2

Answer 38

more ppts to recruit | may be unexpected differences between the ppts

Question 39

two ways to create groups in between-subjects design?

Answer 39

random assignment | matching procedure followed by random assignment

Question 40

what is random assignment? | what is the obejective of it?

Answer 40

every ppt has an equal change of being placed in any of the groups objective to spread individual differences across the groups

Question 41

what is the matching procedure?

Answer 41

1) get a score for each person on the matching variable 2) arrange scores from lowest to highest 3) create pairs of scores of those closest to each other 4) for each pair randomly assign one to one group and the other to the other

Question 42

conditions for the matching procedure?

Answer 42

must have reasons to believe matching variable will have effect on DV must be an accurate way of measuring variable

Question 43

when is within-subjects design used?

Answer 43

conditions require brief time to test but extensive preparation population of interest is small

Question 44

advantages of within-subjects design? x2

Answer 44

more data for each ppts | reduced error variance

Question 45

disadvantages of within-subjects design?

Answer 45

threats to internal validity (testing effects, maturation etc) order effects

Question 46

which order effects are there?

Answer 46

practice effects - improve due to practice fatigue effects - reduced due to fatigue carryover effect - one sequence of condition produces different result than aother sequence

Question 47

how to control order effects?

Answer 47

counterbalancing

Question 48

what is counterbalancing?

Answer 48

using more than one sequence of conditions

Question 49

what are the two types of counterbalancing?

Answer 49

complete | partial

Question 50

what is complete counterbalancing?

Answer 50

every possible sequence is used at least once

Question 51

what is partial counterbalacing?

Answer 51

using a subset of the total number of sequences - randomising order of condition for each ppt or sampling from list of possible sequences latin square

Question 52

what is experimenter bias and how to overcome it?

Answer 52

due to knowing hypothesis of study, experimenter may subconsciously help ppts guess the hypothesis double-blind procedure so don't know which condition is being tested

Question 53

what are the two types of subject bias?

Answer 53

hawthorne effect | demand characteristics

Question 54

what is the hawthorne effect?

Answer 54

ppts change behaviour as they know they are being studied

Question 55

what are demand characteristics?

Answer 55

being a "good subject" by trying to help confirm the hypothesis if they think they know it

Question 56

how to control for subject bias?

Answer 56

deception - keeping ppts naive to purpose of study (reducing demand characetristics) reduces "good subject" effects placebo - conditions where ppts believe they are receiving treatment but they aren't