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Opportunity sample

A sample of participants produced by selecting people who are most easily available at the time of the study.

quota sampling

A nonprobability sampling technique in which researchers divide the population into groups and then arbitrarily choose participants from each group

random sample

a sample in which every element in the population has an equal chance of being selected

snowball sampling

recruitment of participants based on word of mouth or referrals from other participants

self-selecting sample

Sample selected for study on the basis of members' own action in arriving at the sampling point

stratified sampling

A type of probability sampling in which the population is divided into groups with a common attribute and a random sample is chosen within each group

systematic sampling

A procedure in which the selected sampling units are spaced regularly throughout the population; that is, every n'th unit is selected.

Repeated measures

The same participants are used in all the conditions in an experiment.

Independent measures

experimental design where separate participants take part in each of the conditions

Correlation

A measure of the relationship between two variables

Nominal Data

Data which consists of names, labels, or categories.

ordinal data

Data that is ordered on a scale based system.

Ratio Data

Continuous, interval data with a meaningful zero.

inferential statistics

numerical methods used to determine whether research data support a hypothesis or whether results were due to chance

descriptive statistics

statistical procedures used to describe characteristics and responses of groups of subjects e.g. measures of central tendency.

experiment

A research method in which an investigator manipulates one or more factors to observe the effect on some behavior or mental process

laboratory experiment

Experiment in which conditions are highly controlled in order to establish causal relationships.

quasi-experiment

An experiment in which investigators make use of control and experimental groups that already exist in the world at large.

natural experiment

An experiment in which nature, rather than an experimenter, manipulates an independent variable.

participant observation

a naturalistic observation in which the observer becomes a participant in the group being observed

Non-participant observation

The observer is separate from the people being observed

field experiment

An experiment set up in the real world, usually with participants who are not aware that they are in a study of any kind.

Sign test

An inferential statistical test used in test of difference where the data is nominal and it's a repeated measures design.

Chi-square test

An inferential statistical test for either a test of difference or association where the data is nominal.

Wilcoxon test

Inferential statistic testing the difference of ordinal level data in a repeated measures design.

Mann-Whitney

Inferential statistics used to test for difference with ordinal level data in an independent measures design.

Spearman's rho

A test for correlation when data is at least ordinal level.

Related t-test

Inferential statistic used in a repeated measures design with interval or ratio level data.

Unrelated t-test

Inferential statistic used in an independent measures design with interval or ratio level data

Pearson's r

Inferential statistic used to measure a correlation between two interval level co-variables.

EEG (electroencephalogram)

shows brain's electrical activity by positioning electrodes over the scalp

CAT scan (computerized axial tomography)

a method of creating static images of the brain through X rays

MRI (magnetic resonance imaging)

a technique that uses magnetic fields and radio waves to produce computer-generated images of soft tissue. MRI scans show brain anatomy.

fMRI (functional MRI)

A technique for revealing bloodflow and, therefore, brain activity by comparing successive MRI scans. fMRI scans show brain function.

PET scan (positron emission tomography)

Aa visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task

alternative hypothesis

The hypothesis that states there is a difference between two or more sets of data.

Directional hypothesis (one-tailed)

States the direction of the difference or relationship

Non-directional hypothesis

Simply states that there is a difference but not what the difference will be.

null hypothesis

the hypothesis that there is no significant difference between specified populations, any observed difference is due to sampling or experimental error.

independent variable

The experimental factor that is manipulated; the variable whose effect is being studied.

dependent variable

The measurable effect, outcome, or response in which the research is interested.

Co-variables

The variables investigated within a correlation e.g. height a weight.

content analysis

the systematic coding and objective recording of data, guided by some rationale

structured interview

a research procedure in which all participants are asked to answer the same questions

Semi-structured interview

There is a list of questions that have been worked out in advance but interviewers are also free to ask follow up questions when they feel it is appropriate.

case study

a descriptive technique in which one individual or group is studied in depth usually using a range of research techniques.

brain scans

A technique used to investigate the functioning of the brain by taking images of the living brain.

longitudinal study

research in which the same people are restudied and retested over a long period

cross-sectional study

A study in which a representative cross section of the population is tested or surveyed at one specific time.

self-report

a method in which people provide subjective information about their own thoughts, feelings, or behaviours, typically via questionnaire or interview

target population

the total group to be studied or described and from whom samples may be drawn

sampling frame

list of individuals from which a sample is actually selected

Event sampling

the observer records all instances of a particular behaviour.

time sampling

a measurement of the presence or absence of behaviour within specific time intervals

matched pairs design

A method of assigning subjects to groups in which pairs of subjects are first matched on some set of characteristics and then individually assigned randomly to groups.

line graph

a graph that uses one or more lines to show changes in statistics over time or space

Histogram

A graph of vertical bars representing the frequency distribution of a set of data.

Bar charts

Used when data is divided into categories (discrete data)

The bars are separated to show different categories

pie chart

a circular chart divided into triangular areas proportional to the percentages of the whole

scatter diagram

a graph that shows the degree and direction of relationship between two variables

normal distribution

describes a symmetrical, bell shaped curve that shows the distribution of many physical and psychological attributes

Positive skewed distribution

Most of the scores are bunched towards the left. The mode is to the left of the mean because the mean is affected by the extreme scores tailing off to the right.

negative skewed distribution

Most of the scores are bunched towards the right. The mode is to the right of the mean because the mean is affected by the extreme scores tailing off to the left.

mean

the arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores

Median

the middle score in a distribution; half the scores are above it and half are below it. If there are two middle values then add together and divide by 2.

Mode

The value that occurs most frequently in a given data set.

range

the difference between the highest and lowest scores in a distribution

Standard Deviation (SD)

A measure of the variability of a data set, calculated as the square root of the variance (V).

peer review process

a way in which scholars evaluate research manuscripts before they are published in order to ensure their quality

internal reliability

different parts of the same test produce similar results

External reliability

A measure of consistency over several different occasions.

inter-rater reliability

measure of agreement among observers on how they record and classify a particular event

test-retest reliability

a method for determining the reliability of a test by comparing a test taker's scores on the same test taken on separate occasions

split-half reliability

dividing the test into two equal halves and assessing how consistent the scores are

internal validity

the degree to which changes in the dependent variable are due to the manipulation of the independent variable

external validity

the extent to which the results of a study can be generalized to other situations and to other people

researcher bias

Changes in participants' behavior caused by the unintended influence of a researcher's actions.

demand characteristics

Any aspects of a study that communicate to the participants how the experimenter wants them to behave.

social desirability bias

the tendency for people to say what they believe is appropriate or acceptable

concurrent validity

the degree to which the measures gathered from one tool agree with the measures gathered from other assessment techniques

predictive validity

Refers to the function of a test in predicting a particular behavior or trait.

face validity

Measures whether a test looks like it tests what it is supposed to test.

content validity

the extent to which a test measures the behavior that is of interest

construct validity

the extent to which a tool measures what it's supposed to measure

active deception

deliberately misleading research participants by giving them false information

passive deception

withholding information from the research participants by not giving them all the details of the experiment

Valid consent

Participants must be given comprehensive information concerning the nature and purpose of the research and their role in it, in order that they can make an informed decision about whether to participate.

Confidentiality

Keeping the identity of the participants anonymous and their data safely secured

ethics committee

A group of people within a research institution that must approve a study before it begins.

BPS

British Psychological Society

Ethical Guidelines

suggested rules for acting responsibly and morally when conducting research or in clinical practice.

significance level

A critical probability associated with a statistical hypothesis test that indicates how likely an inference supporting a difference between an observed value and some statistical expectation is true.