Psych Scientific Method

Theory

An integrated set of principles that organizes and predicts behavior.

Hypothesis

A testable prediction often implied by a theory.

Operational Definition

Statements (descriptions) of the procedures used to define research variables.

Replication

Repeating the essence of a study, usually with different participants and in different situations.

Hindsight bias

The tendency to believe, after learning the outcome, that you knew that was how it would turn out.

Goals of Research

To describe, predict, & explain behavior.

Case Study

A descriptive technique in which one person is studied in depth in the hope of revealing universal principles.

Naturalistic Observation

Observing & recording behavior in naturally occurring situations without manipulating or controlling the situation.

Survey

 A technique for obtaining self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of them.

Population

All of the people in a particular group from which a sample may be drawn.

Random Sample

subset of people who fairly represent the population because each person has an equal chance of being selected. increases the generalizability of study.

Simple Random Sampling

Randomly picking individual names

Cluster Random Sampling

Randomly picking naturally occurring groups of people (Homerooms)

Stratified Random Sampling

First dividing the population into groups and then randomly picking individuals from those groups (Race, gender, grade, etc)

Nonrandom Sampling

Not everyone in the population has an equal chance of being picked. Also called convenience sampling. Because of this there would be SAMPLE BIAS

Generalizability

The extent to which results of a study can be applied to the outside world.  

False Consensus Effect

 The tendency to overestimate the extent to which others share our beliefs and behaviors.

Social Desirability Bias

Tendency of subjects to present themselves in a socially desirable light.

Correlational Research

Research that seeks to measure the RELATIONSHIP between two variables without trying to determine causality or manipulating either of the variables.

Scatterplot

A graphed cluster of dots, each which represents the values of two variables.  The slope of the dots represents the direction (+ or -) of the relationship while the amount of "scatter" suggests the strength of the correlation.

Correlation Coefficient

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

Always between -1.00 and +1.00

 correlations cannot tell us that one variable CAUSES changes in the other

A Positive correlation coefficient

as one variable increases, so does the other.

A Negative correlation coefficient

as one variable increases, the other decreases (i.e., an inverse relationship)

Illusory Correlation

The perception of a relationship between two variables where none truly exists.

The True Experiment

A research method in which an investigator manipulates one or more factors (independent variables) in order to observe the effect on some behavior or mental process (dependent variable).  By randomly assigning participants to groups, other relevant factors are controlled.

Independent Variable

The factor that is being manipulated by the researchers. The theoretical "cause" in the cause and effect relationship

Dependent Variable

The factor (a behavior or mental process) that is being measured by the researchers. The variable that is predicted to change in response to the manipulation of the IV.

Random Assignment

Assigning participants to control and experimental conditions on the basis of chance, thus minimizing pre-existing differences between the groups (i.e., it controls preexisting subject variables.

Experimental Condition

The condition of an experiment that exposes participants to the treatment of interest, that is, to one level of the independent variable.

Control Condition

The condition of an experiment that contrasts with the experimental condition and serves as a comparison for evaluating the effect of the treatment.

Placebo

An inert substance given to the control group in place of an actual medication. It controls the Placebo Effect.

Double-Blind Design

An experimental procedure in which both the research participants and the research staff are (blind) about whether subjects are in the control or experimental groups

(commonly used in drug-evaluation studies).

Controls subject and experimenter effects.

Subject Effects or Biases

Any response by subjects in a study that does not represent how they would normally behave if not under study. (placebo effect and the demand characteristics of the study)

Demand Characteristics

Aspects of the study that suggest to the subjects what type of behavior is expected or desired by the researchers.

Experimenter Effects or Biases

Any behavior of a researcher that might affect the behavior of the subjects or affect the measurement and recording of the dependent variable.

Ex Post Facto

Designs similar to true experiments, but without all of the control techniques built in (e.g., random assignment may not be used).

Measures of Central Tendency

Mean, Median and Mode

Measures of Variability

Range, Variance and Standard Deviation

Range

Difference between the largest and smallest scores in a distribution. Most affected by outliers

Variance

A statistical average of the amount of dispersion around the mean in a distribution of the scores. It is the Standard Deviation squared

Standard Deviation

A statistical measure of the amount of dispersion in a set of scores. Specifically, it is the square root of the average squared deviations from the mean of a set of scores. It is simply the square root of the variance.

Normal Curve

Hypothetical, bell-shaped distribution of scores that occurs when a normal distribution is plotted as a frequency polygon.

In a normal distribution, the mean, median, and mode are all equal and divide the distribution in half (the 50th percentile).

Percentile Rank

Reflects the percentage of subjects who score lower than the subject in question

Positively Skewed Distribution

A distribution where most scores are clustered at the lower end of the curve, with a few very high scores creating a long "tail" to the right.

The mean is greater than the median, and the median is greater than the mode.

Negatively Skewed Distribution

A distribution where most scores are clustered at the upper end of the curve, with a few very low scores creating a long "tail" to the left.

The mean is less than the median, and the median is less than the mode.

Statistical Significance

Probability that the results obtained were due to chance (represented by the value of 'p').

p-value of .05 or less means that results were statistically significant (i.e., not due to chance).