Research Methods

hindsight bias

the tendency to believe, after learning an outcome, that one would have foreseen it

double-blind procedure

research participants and the research staff are ignorant (blind) about whether the research participants have received the treatment or a placebo.

case study

an observation technique in which one person is studied in depth in the hope of revealing universal principles

random sampling

a sample that fairly represents a population because each member has an equal chance of inclusion

random assignment

assigning participants to experimental and control groups by chance, thus minimizing preexisting differences between those assigned to the different groups

Correlation

A measure of the extent to which two factors vary together, and thus of how well either factor predicts the other.

correlation coefficient

a statistical index of the relationship between two things (from -1 to +1)

experiment

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

independent variable

variable that is manipulated

dependent variable

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

placebo effect

improvement resulting from the mere expectation of improvement

control group

the group that does not receive the experimental treatment.

operational definition

a carefully worded statement of the exact procedures used in a research study. Important for replication.

statistical significance

a statistical statement of how likely it is that an obtained result occurred by chance

normal curve

the bell-shaped curve that describes the distribution of many physical and psychological attributes. Most scores fall near the average, and fewer and fewer scores lie near the extremes

postive skew

tail to the right

negative skew

tail to the left

Population vs. Sample

The population is the whole group while a sample are parts of the population.

mean

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

Mode

the most frequently occurring score(s) in a distribution

Median

the middle score in a distribution; half the scores are above it and half are below it

confounding variable

a factor other than the independent variable that might produce an effect in an experiment

Histogram

a bar graph depicting a frequency distribution

naturalistic observation

observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation.

Scatterplot

a graphical depiction of the relationship between two variables - used with correlational studies.

Hypothesis

A testable prediction, often implied by a theory

postive correlation

a relationship between two variables in which both variables either increase or decrease together

negative correlation

as one variable increases, the other decreases

Experimental vs. Correlational

causation vs. relationship strength

research ethics

informed consent, confidentiality, debriefing, no harm, avoid deception, avoid coercion.

standard deviation

a computed measure of how much scores vary around the mean score. Calculated as the square root of the variance.

experiemental group

in an experiment, the group exposed to the treatment, that is, to one version of the independent variable

meta-analysis

a procedure for statistically combining the results of many different research studies

Quantitative Data

numerical data

Qualitative Data

descriptive data (interviews)

Informed Consent

an ethical principle that research participants be told enough to enable them to choose whether they wish to participate

Debriefing

a verbal description of the true nature and purpose of a study

Effect Size

the magnitude, or strength, of a relationship between two or more variables