Lecture 7, 8, 9: Experimental Research and Design

Question 1

A well designed experiment must meet what three requirements?

Answer 1

a.) at least one IV that is manipulated (why?–> important to be able to assess the effects on the participants responses)

b.) Random assignment to a condition (why?–>ensures their initial equivalence)

c.) Control over all extraneous variables

Question 2

instructional manipulation

Answer 2

vary IV through instructions or information that participants receive

*elaborate instructional manipulation= studies that aim to change peoples thoughts motions or behaviors

Question 3

invasive manipulation

Answer 3

creating physical changes in the participants body through physical stimulation (drug administration. surgery etc.)

Question 4

environmental manipulation

Answer 4

experimental modifications of aspects of the research setting

ex: a researcher interested in visual perception might vary intensity of illumination

Question 5

What are the advantages of a WITHIN SUBJECTS repeated measures design ?

Answer 5

increase in power and the possibility of having a smaller sample size

Question 6

What are order effects? Describe all three

Answer 6

participants behavior is affected by the order in which they participate in the various conditions of the experiment

practice effects: when participants performance improves merely because they complete the dv several times

fatigue effects: participants become tired bored or less motivated as the experiment progresses

sensitization: after receiving several levels of the IV and completing the dv several times participants within subjects design may begin to deduce what the hypothesis is –> different responses that they did before

Question 7

What is counterbalancing

Answer 7

used to guard against oder effects by presenting the levels of the IV in different order to the participants

Question 8

what are carryover effects

Answer 8

effect of a treatment condition persist after the condition ends ; when the effects of one level of the IV is still present when another IV is introduced

Question 9

What is treatment variance

Answer 9

portion of the variance in participant scores on the DV due to the IV

Question 10

what is confound variance

Answer 10

portion of the participants variance in dv scores due to extraneous variables that differ between experimental groups

Question 11

the presence of _____varriables threatens the ________ validity of a study

Answer 11

confounding ; internal

Question 12

There are a few major common effects to the internal validity of an experiment describe them:

biased assignment:

differential attrition:

pretest sensitization

history effects

Answer 12

biased assignment: participants are assigned to groups in a nonrandom manner –> systematic differences before introduction of the IV

differention atrition : uneven loss of participants from a study–> loss is not random across all conditions

pretest sensitization: completion of a pretest impacts the participants posttest response –> was the response really due to the IV or was it pretest sensitization?

history effects: results of s study being impacted by outside extraneous events

Question 13

expectations can compromise the internal validity of an experiment; describe the following: expectancy effects, demand characteristics, and placebo effects

Answer 13

expectancy effects: researchers expectations on the outcome of the study effect the participants responses–> the researchers see what they want to see rather than what is actually occurring

demand characteristics: aspects of the study indicate to participants how they should behave causing behavior changes

placebo effects: a change the occurs as a result of mere belief that the change will occur: participants receive a treatment and improve only because they belief they are receiving a valid treatment

Question 14

what are the main factors that lead to error variance: name, describe, and prevention method

Answer 14

individual differences: preexisting differences between participants when they enter a study
–> solution = use a homogenous sample of participants b/cthe more alike participants are the less error variance is produced by their differences

transient states: current behavior or feeling of a participant on the day of completing the survey
–> avoid creating more differences in transient states throughout the experiment

environmental factors: differences in the environment which the study is conducted. ex: phone buzzing, pen clicking, loud breathing etc.
–> try to ensure setting is as invariant as possible when different participants are being tested

differential treatment: researches not realizing they are treating participants differently
–>automate experiment as much as possible/ record instructions so it can be delivered the same way to all participants

measurement error: the measures that are being used are not accounting for what the researchers want them to account for–> measures could be outdated, falty bc they work well with certain groups than others

Question 15

External validity is important because it focuses on?

Answer 15

refers to whether the findings of the study can be generalized and replicated

Question 16

What is a key contributor to external validity ?

Answer 16

random sampling **different than random assignment

Question 17

what is the “experimenters’ dilemma”?

Answer 17

the greater the internal validity the lower the external validity

the more control the experimenters place on the experiment the less replicable/generalizable the findings become in real world contexts

Question 18

describe simple random assignment

Answer 18

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

Question 19

describe matched random assignment

Answer 19

pretest measure of the DV allows researchers to match participants into homogenous blocks then those blocks are randomly assigned to conditions

Question 20

it is important that independent variables have ___ or more levels; in other words, this means …

Answer 20

2; independent variable must have 2 or more conditions; ex: 4 levels of caffeine doses

Question 21

what are the three types of independent variables

Answer 21

environmental, instructional, invasive

Question 22

describe the experimental group vs the control group ?

Answer 22

the control group consists of participants that receive a zero level of the IV

the experimental group consists of participants that receive the nonzero level of the IV

Question 23

TRUE or FALSE : researchers always need to include a control group

Answer 23

FALSE; its up to them to decide if it will help them interpret the results

Question 24

what is a pilot test and why do researchers use it?

Answer 24

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

its used to ensure the levels of the IV are different enough to be detected by participants NOT USED to check if hypothesized effects will be produced

Question 25

what is a manipulation check

Answer 25

a question or set of questions designed to determine whether the IV was successfully manipulated

ex: ask participants to rate brightness of a lightbulb if they can rate the brightness of the lights differently –> differences in brightness is perceivable

Question 26

participant variables

Answer 26

characteristics of participants non changeable by the researcher

ex: gender race

Question 27

TRUE or FALSE: most experiments have several dependent variables

Answer 27

true

Question 28

a one way design is a design in which _____. A two group experimental design is______

Answer 28

only one IV is manipulated

simplest one way design where the IV has two levels/there are two conditions

Question 29

Randomized group design

Answer 29

participants randomly assigned to one of two or more conditions

Question 30

within subjects design

Answer 30

each participants serves in all conditions

Question 31

post test designs are ones that

Answer 31

only measure the DV at the end of experimental manipulation

Question 32

what is a pre-test post test design

Answer 32

a design that measures the DV before and after the introduction of the IV

Question 33

what are three major benefits to the pre-test posttest designs

Answer 33

1. researcher can verify participants did not differ in respect to the DV at the beginning of the experiment/ can confirm random assignment
2. comparison of pre and post test scores allows analysis of the exact change in scores of a participant
3. more powerful thus more likely to detect the effects of the IV on the DV–> error variance due to preexisting differences can be ruled out

Question 34

Drawbacks of pretests include?

Answer 34

pretest sensitization –> sensitize participants responses, they may behave differently than they normally would have

Question 35

Describe a factorial design

Answer 35

an experimental design in which two or more IV are manipulated

iv-factors

Question 36

Interpreting factorial designs

2x2 means what
4x2 means what

2x2x4 means what

Answer 36

the design has two independent variables each of which has two levels

the design has two independent variables one with four levels and one with two levels

the design has three IV the first two have 2 levels and the third has 4 levels

Question 37

whats the primary advantage of factorial designs over one way designs?

Answer 37

they provide information on the separate effects of each IV and the combined effects of them

as well as information on if variability is due to error variance

Question 38

main effect

ex: in a 2x2 we can examine__ main effects

Answer 38

the effect of a single IV in a factorial design

2 main effects one for each IV

Question 39

when is an interaction present?

Answer 39

when the effect of one IV differs across the levels of other IV

if variable A has the same effect on participants responses no matter what level of variable B they receive there is no interaction present

Question 40

describe an expericorr design

Answer 40

used to examine the generality of the IVs effect

allow researchers to determine if the effects of the IV occur for all participants or only for participants with certain attributes

Question 41

between subjects group design vs within subjects design

Answer 41

participant participates in only one condition

participant participates in every condition

Question 42

power of an experimental design refers to what?

Answer 42

its ability to detect effects of the IV

Question 43

how can you combat expectancy effects?

Answer 43

–> can be avoided by the double blind procedure where neither the researcher nor the participants know the full extent of whats being studied

Question 44

how can one eliminate demand characteristics?

Answer 44

–> conceal the real purpose of the experiment and eliminate any cues that could hint

double blind procedure

Question 45

General tips for minimizing error variance include

Answer 45

homogenous sample

equal treatment at all times

hold lab conditions constant

standardize research procedures

automate the experiment as much as possible

use only reliable measurement procedures

Question 46

Higher order factorial designs _______

Answer 46

involve more than two IV