Psychological Statistics || Module 5 & 6

Hypothesis

Presumptive statement seeking proof in an investigation.

Assumption

Taking things for granted to simplify logical procedures.

Postulate

Working belief accepted at face value in scientific activity.

Null Hypothesis

Assumed true unless data convincingly prove it false.

Alternative Hypothesis

Accepted only if data convincingly support its truth.

Significance Level

Threshold set pre-data collection to determine hypothesis rejection.

Rejection Region

Values of test statistic leading to null hypothesis rejection.

One Tailed Test

Alternative hypothesis is directional, specifying a single direction.

Two Tailed Test

Alternative hypothesis does not specify departure from null hypothesis.

Critical Value

Value corresponding to a specific rejection region in hypothesis testing.

Test Statistic

Inferential statistic used to test a null hypothesis.

Z-Score

Measure of how many standard deviations a data point is from the mean.

Hypothesis Testing Process

Four-step procedure to test hypotheses in a structured manner.

Population Mean

Average value of a specific group in a population

Population Standard Deviation

Measure of the amount of variation in a population

Critical Values

Values used to determine rejection of the null hypothesis

Two-Tailed Test

Hypothesis test looking for differences in both directions

P-Value

Probability of obtaining results at least as extreme as the observed results

T-Statistic

Statistic used in T tests to support or reject the null hypothesis

Degrees of Freedom

Number of independent values or quantities which can be assigned to a statistical distribution

T Distribution Table

Table listing critical values for T tests at different levels of significance

One Sample T-Test

Test to compare one population mean using a single sample

Dependent Samples

Samples that are related or paired in some way

Independent Samples

Samples that are not related or paired

Longitudinal Data

Data from same participants at different time points

Dependent Samples T-Test

Compares means from the same group measured twice

Difference Scores

Scores calculated by subtracting paired values

Assumptions for Dependent Samples T-Test

Continuous dependent variable, matched pairs, no outliers

Independent Samples T-Test

Compares means from two separate groups

Homogeneity of Variances

Equality of variances in different groups being compared

Pooled Variance

Combined variance of two independent samples

Standard Error

Measure of the variability of sample statistic

Sum of Squares

Sum of squared deviations from the mean

Continuous Scale

Measurement scale with equal intervals and a true zero point

Spurious Outliers

Outliers that do not represent true data patterns

Standard Deviation

Measure of the dispersion of a set of values

One-Tailed Test

Test that looks for a difference in one direction only

Raw Scores

Original data values before any transformation

Mean

Average value of a set of numbers

Interval Measurement

Measurement scale with equal intervals but no true zero

Ratio Measurement

Measurement scale with equal intervals and a true zero

Matched Pairs

Participants present in both groups being compared

Levene's Test

Test for homogeneity of variances in statistical analysis

Near-to-Normal Distribution

Data distribution closely resembling a normal distribution

Degrees of Freedom Calculation

Determining the number of independent values in a calculation