Oxford Text pg 9-19

confounding variables

confounding variables

variables that can potentially distort the relationship between the IV and the DV

target population

the group of people to which the findings of the study are expected to be generalized

sample

the group of people taking part in the experiment itself

representatives

the key property of a sample

participant characteristics

whatever can theoretically influence the relationship between the IV and DV

sampling techniques

a process of sampling that depends on the aim of the research, available resources, and the nature of the target population

random sampling

a process of sampling that depends on the aim of the research, available resources, and the nature of the target population

stratified sampling

a theory-driven approach where you first decide the essential characteristics the has to reflect, then study the distribution of these characteristics in the target population, then recruit participants that keep the same proportions

convenience (opportunity) sampling

a process of sampling where you recruit participants that are most easily available

self-selected sampling

a process of sampling of recruiting volunteers

independent measures design

random allocation of participants into groups and a comparison between these groups

matched pair design

an experimental design of using matching to allocate participants into groups and comparing between groups

matching variable

the variable controlled in a matched pair design

repeated measure design

an experimental design where the goal is to compare conditions rather than groups of participants

order effects

results may be different depending on which condition comes first (practice and fatigue)

counterbalancing

using other groups of participants where the order of the conditions is reversed

participant variability

differences between the groups before the experiment starts

construct validity

a type of validity that characterizes the quality of operationalizations (the phenomenon is first defined as a construct and then expressed in terms of observable behavior)

internal validity

a type of validity that characterizes the methodological quality of the experiment

external validity

a type of validity that characterizes the generalizability of findings in the experiment

population validity

the extent to which findings can be generalized from the sample to the target population

ecological validity

the extent to which findings can be generalized from the sample to the target populations

selection

a threat to internal validity where groups are not equivalent at the start of the experiment (apart from planned IV difference)

history

a threat to internal validity where outside events happen to participants in the course of the experiment

maturation

a threat to internal validity where participants go through natural development processes like fatigue or growth

testing effect

a threat to internal validity where the first measurement of the DV may affect the second (and subsequent) measures

instrumentation

a threat to internal validity where the instrument measuring the DV changes slightly between measurements

regression to the mean

a threat to internal validity where the initial score on the DV is extreme (either high or low) and therefore are more statistically likely to become more average

experimental mortality

a threat to internal validity where some participants drop out during an experiment (problematic if dropouts aren’t random)

demand characteristics

a threat to internal validity where participants understand the purpose of the experiment and change their behavior subconsciously to fit that interpretation

experimenter bias

a threat to internal validity where the researcher unintentionally exerts an influence on the results of the study

double-blind designs

information that could introduce bias is withheld both from participants and from the people conducting the experiment

quasi-experiments

experiments where pre-existing inter-group differences are used for allocation into groups

field-experiments

experiments that are conducted in a real-life setting

natural experiment

experiments conducted in participants’ natural environment but the researcher has no control over the iV

Rodin & Piliavin’s Subway Study

the researchers pretended to collapse on a subway train and observed if other passengers would come to help

• IV = cane condition or drunk condition