Helpful Psychology/Statistical Terms This ar is based on the navard in Keppel, Saufley and also Tokunaga, Introduction come Design and Analysis

Alternative Hypothesis: The hypothesis that is accepted if the null hypothesis is rejected, usually stood for by the symbol H1. Also known as the experimental or research study hypothesis. The alternative hypothesis usually claims that the independent variable has had actually an result on the dependency variable that cannot be explained by opportunity alone. ( N.B. You never ever prove that the alternative hypothesis is correct, also if the null hypothesis is rejected, there is always a chance that you have actually wrongly garbage it.)

Between topics design: one experimental architecture in i beg your pardon each subjects is randomly assigned to only one of the therapy conditions.

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Case-study: A research technique involving the comprehensive study of a solitary individual, used greatly in clinical psychology and neuropsychology.

Control Group: A team of subjects which walk not receive the experimental treatment but in all various other respects is cure in the same means as the speculative group, (so regarding tease the end the effects of the treatment itself). In clinical studies including the administration of drugs the control group is recognized as the placebo group. A neutral problem ( placebo ) is administered to this group without the subjects learning if that is an active drug or not.

Correlational design: A kind of research style in which fads of correlations room analyzed.

Dependent Variable: The selected behavior, i beg your pardon is measure up to try to gauge the impact of the independent change in an experimental design.

Descriptive Statistics: Data summary in number form, such as mean, median, mode. This develops the an initial stage that data analysis. Means, typical deviations and also standard errors room presented in the kind of a table.

External Validity: The level to which outcomes of a study with a sample the subjects have the right to be generalized to make statements about a lot larger populace of subjects.

F-ratio: A statistical index relating organized variation in the data (caused by treatment effects plus arbitrarily error) to unsystematic variability in the data (caused by random error alone). The results of therapies plus error is the numerator and also the effect of error (chance) is the denominator that the F-ratio

Independent Variable: The variable manipulated by the experimenter. It is a attribute of a task offered to subjects, or a manipulation of the external or interior environment. Internal atmosphere refers come attitudes, ideas etc.

Inferential Statistics: Procedures and measures used to do inferences about population characteristics indigenous samples attracted from that population. The process of hypothesis experimentation is part of inferential statistics.

Longitudinal Study: A type of research regularly used come study, e.g., developmental worries where the team of subjects is studied over an extended period of time. Dimensions are taken numerous times at regular intervals come look at the impact of time on the dependency variable.

Matched-Subjects Designs: A class of between-subjects architecture in i m sorry the subjects room matched on one or more relevant characteristics. This design is supplied to reduce between groups variability.

Mean: A measure of main tendency, providing an median of a collection of scores (i.e. The amount of every the scores divided by the variety of scores in the set).

Median: measure up of main tendency, providing the value of the middlemost score (above or below which fifty percent of all the scores lie). If over there is an even variety of scores the median is the median of the two middle scores.

Naturalistic Observation: A kind of observational research in which the observer documents information around naturally emerging behavior if attempting not to intervene or affect the habits in any kind of way. This research study is also described together unobtrusive.

Nominal scale: Data is allocated into different (often named or numbered) categories. Because that example, the allocation of books in a library catalogue to various topics. Data top top this range cannot it is in meaningfully included and subtracted.

Null hypothesis: This is generally a declare of "no effect", that is come say that the independent variable will certainly not have any kind of effect ~ above the dependency variable and also that any type of differences between the experimental and also control groups are attributable come chance. The null theory is usually stood for by the symbol H0, and also is proclaimed in order that it deserve to be rejected as an explanation for the results of the experiment.

Observational Research: The systematic examine of behavior as it wake up in the organic environment.

Ordinal scale: A scale of measurement where data are put in order, however where there is no resolved amount of difference between the point out on the scale. Because that example, the location order the premier organization football teams, or civilization ranking that tennis players.

Placebo effect: A hopeful or therapeutic advantage resulting indigenous the management of a placebo to someone who believes the treatment is real.

Random sampling: A procedure in which each member that the population has an equal chance of being consisted of in the sample.

Reliability: The consistency through which a measuring instrument (such together a psychometric test) performs its" function, gauged, because that example, by comparing check scores indigenous the very same subjects at different times.

Significance (statistical): Is achieved when there is a short probability that the results of an experiment occurred by opportunity alone. In psychology it is standard that results are claimed to be far-ranging if the probability the their occurrence by opportunity is equal to or much less than 5 per cent or 0.05

Significance Level: The probability through which the experimenter is ready to disapprove the null hypothesis ( in donate of the alternate hypothesis ) when the null hypothesis is in truth correct. Likewise known as the probability the a type I error.

Standard Deviation: A measure of dispersion within a collection of data, calculated from the square source of the variance, to offer a worth in the same range as raw scores. The conventional deviation is the spread of scores approximately the typical of the sample.

Standard Error: The traditional deviation of the sampling circulation of the mean. A statistical estimate of the populace standard deviation based on the mean and standard deviation that one sample. Calculation by separating the standard deviation that the sample by the square source of the number of subjects in the sample. T-test: A parametric statistics test the the difference in between the means of two samples.

Type ns Error: one error of statistics inference when null hypothesis is rejected once it is true. This is one error that "seeing too much in the data."

Type II Error: an error of statistics inference when the null theory is retained when it is false. This is an error that "not seeing enough in the data."

Validity: native the Latin validus, (strong), the degree to which a measure up instrument measures what it is claimed to measure.

Variability: The degree to which distinctions exist among a collection of scores. The traditional deviation is usually provided to define the variability of scores in a sample.

Variable: A residential property that have the right to take different values. In study designs variables room classed as independent and also dependent.

Within-Groups Variability: A measure of variability based on the variation of subjects treated alike in one experiment, ( i.e. The subjects are in the same group ). The amount of within-groups variability offers a measure of speculative error.

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Within-Subjects Design: an experimental architecture where all subjects get all therapy conditions. Also called a repeated procedures design.

Z-score: A score express in devices of standard deviations from the mean. Likewise known as a typical score


Keppel, G., Saufley, W. H. & Tokunaga (1992). Development to design and analysis: A student"s handbook (2nd ed.). Brand-new York: W. H. Freeman and Company.