Ninth Edition CoverGraziano & Raulin
Research Methods (9th edition)

Glossary Items Starting with "M"

A characteristic of the abstract number system in which the numbers have an inherent order.

main effects
In a factorial design, main effects refer to the individual effects of the independent variables. In contrast, interaction effects are the combined effects of two or more independent variables on the dependent variable.

mainstream psychology
Contemporary psychology, which is largely an integration of many of the earlier schools of psychology and their theoretical models.

manipulated factors
Independent variables in a factorial design in which the levels of the factors are determined by active manipulation by the experimenter.

manipulated independent variable
Type of independent variable found in an experimental research study. When manipulated independent variables are used, participants are randomly assigned to groups or conditions.

The explicit control of the independent variable by the researcher.

manipulation check
Procedure designed to verify that the independent variable varied in the different groups or conditions. A manipulation check is independent of any evaluation of the effect of the independent variable on the dependent variable.

Mann-Whitney U-test
A nonparametric inferential statistic used to test the difference between two groups when the dependent measure produces ordinal data.

matched-pairs t-test
See correlated t-test.

matched random assignment
Experimental procedure used to insure that groups are equivalent at the beginning of the study. In matched random assignment, participants are matched in small groups (size is determined by the number of conditions in the study) on relevant variables, and each member of the matched group is randomly assigned to one of the conditions of the study until all members have been assigned to one condition. Matched random assignment is an alternative to a within-subjects design and should be used whenever significant sequence effects can be expected in a within-subjects design.

matched-subjects design
Research design in which participants are matched on a variable that is highly correlated with the dependent measure. Once matched, each participant is randomly assigned to each of the groups defined by the independent variable. The design helps control for individual differences without introducing the sequence effects inherent in a within-subjects design.

materials subsection
See apparatus subsection.

matrix of cells
Structure of cells in a factorial design.

Potential confounding factor involving changes in participants on the dependent measure during the course of the study that results from normal growth processes.

Arithmetic average of scores. The mean is the most commonly used measure of central tendency but should be computed only for score data.

mean square
In analysis of variance (ANOVA), the mean square is a variance estimate. Several different mean squares are computed in any ANOVA. It is the ratio of mean squares that is the F-ratio.

measurement error
Any inaccuracy found in the measurement of a variable. Although it is impossible to determine the precise degree and direction of measurement error for a given participant, it is possible to specify the average error associated with a particular measure.

measurement reactivity
Any effect on the participant's behavior that results from the participant being aware that he or she is being observed. Measurement reactivity can be reduce by using unobtrusive measures.

measures subsection
See apparatus subsection.

measures of central tendency
Descriptive statistics that indicate the typical score.

Middle score in a distribution.

Based on the subject experience of a person rather than objective behavior.

A procedure that allows the statistical averaging of results from independent studies of the same phenomena. Meta-analyses essentially combine studies on the same topic into a single large study, providing an index of how strongly the independent variable affected the dependent variable in the set of studies.

method section
The section of the research report that details the nature of the sample and the procedures used in the study.

Tiny tubes that can be surgically implanted in animals. These tubes allow the animal to function normally, with no pain or discomfort, while at the same time allowing researchers to study brain functioning by delivering specific chemicals to specific regions of the animals brain to see their impact on functioning. 

A procedure similar to micro-iontophoresis except that the tiny tubes are actually one tube inside of another, with the outer tube having a porous tip. This permits the researcher to pump substances through the tube, allowing the natural chemicals of the brain to be sampled through the porous end of the tube. This process permits researchers to see what chemicals are produced and active in specific brain regions while the animal is performing specific tasks and, thus, helps researchers to understand potential biological mechanisms behind specific behavior.

A procedure involving the implantation of tiny tubes or microcannula into specific regions of the brains of animals. This process can be done without causing pain to the organism. It allows the researcher to deliver specific chemical substances to specific regions of the brain in order to see what impact the chemicals have on the functioning of the animal.

Computer package for statistical analysis of data.

mixed designs (between- and within-subjects variables)
Factorial design in which at least one of the factors is a between-subjects factor and at least one of the factors is a within-subjects factor. The pattern of between- and within-subjects factors affects the selection of the statistical analysis.

mixed designs (manipulated and nonmanipulated variables)
Factorial design in which at least one of the factors represents a nonmanipulated independent variable and at least one of the factors represents a manipulated independent variable. The distinction between manipulated and nonmanipulated variables does not affect the data analysis. However, the interpretation of the results must take into account the fact that at least some of the factors are nonmanipulated factors and, therefore, represent differential research.

Most frequent score in a distribution.

In science, models are representations of the complex reality of the real world.

moderator variable
Any variable that has an effect on the observed relationship between two or more other variables. When a moderator variable is operating, it is best to measure the relationship between variables separately in subgroups defined by the moderator variable. For example, relationships between variables are often evaluated separately in males and females (a commonly used moderator variable).

Monte Carlo study
A procedure that evaluates the effectiveness of statistical tests by simulating with a computer the repeated sampling of participants from a population with known parameters. The characteristics of the populations can be systematically varied to see what effect these variations have on the accuracy of the statistical decision. This process allows one to determine empirically the probability of Type I and Type II errors to see the strength of the impact of  violations of the assumptions of statistical procedures.

A device for moving the cursor on the screen of a personal computer. Sliding the mouse on a table moves the cursor, and clicking the buttons on the mouse performs various tasks.

multidimensional scaling
A group of statistical methods that are used to simplify data by finding a small number of dimensions or factors that collectively account for most of the variability in a group of scores.

multilevel, completely randomized, between-subjects design
A research design, using more than two groups, in which participants are randomly assigned to groups and each participant appears in only one group.

multiple baseline design
Research design often used with single participants when one wants to infer a causal relationship between the independent and dependent variables. Baselines on several different behaviors are taken, and treatment strategies are applied at different points in time to each behavior being monitored.

multiple-choice items
In a questionnaire, each question or item is presented with several answers from which the respondent chooses one.

multiple correlation
A correlation in which a criterion is correlated with a set of variables. The correlation is computed by finding the linear combination of the set that will provide the highest possible correlation with the criterion.

multiple observers
Control used to evaluate the accuracy of observations made by two or more independent observers.

multivariable design
See factorial design.

Multivariate Analysis of Variance (MANOVA)
Extension of analysis of variance in which two or more dependent measures are simultaneously evaluated.

multivariate correlational designs
Correlational designs that include more than two variables.

multivariate techniques
Advanced statistical procedures used to evaluate complex relationships among several variables.