Full book glossary Flashcards
Interval variable
A variable where the values are numerical and where differences between values are consistent across the range of values
Axes
The horizontal and vertical scales of a graph (see x-axis and y-axis)
Unique effect size
The result of ANOVA analysis. A measure of the effect of each IV on the DV which discards all overlapping covariation. The unique effect size is the contribution made by an IV to a DV that is not made by any other measured IV
Confidence interval
A range of values that a particular statistical value is believed to fall within at a specified level of confidence e.g. 95%
Inter-quartile range
Measure of dispersion used typically for ordinal data; the range of values in the middle two quadrants of a data set
Maximum likelihood
A value of an estimated parameter (mean, coefficient etc.) that has the highest likelihood making it the most likely value
Association
Neutral word to describe a relationship
Direct effect size
The effect size in a linear model between an IV and a DV. It shows how much the DV is changed by a change in the IV
Extraneous variable
An unwanted variable that may be influencing a DV
Model effect size
Effect size of the whole model on the DV
Confirmatory research
Research designed to test a specific hypothesis
ANOVA
Analysis of Variance, type of statistical test that splits variance of DV into its various sources
Covariance
A measure of the joint variability between two variables
Scale
A common way of using numbers to describe quantities. The use of cm to describe the length of things is an example. Other scales can be used for the same purpose (inches, cubits). Scales specify how much the quantity involved must be changed to increase its value by a certain amount
Nominal variable
Another term used for Categorical variables
Outlier
- Authors of new, alternative statistics textbooks
- Also used to describe data points that appear not to belong to the population being studied, either randomly occurring or due to research error
Categorical variable
Variable where data is divided into labelled groups (categories); there is no order to the groups
Likert scale
Ordinal self-report scale used for responses to questions, often with agree – neutral – disagree options
Linear
- Used to describe relationships where both variables plotted together form a straight line
- Also used to describe combinations of variables by addition
Mediation
The possibility that the effect of an IV on a DV occurs through an intermediary (mediating) variable
Variable
Any way in which people/animals/situations differ
2-Tailed Test
Statistical test with no predicted effect size direction
Experimental study
Study which deliberately creates an independent variable, such as dividing participants into active and control groups
Variance
Measure of variability: spread of values, the square of the standard deviation
Order effects
Within-participants design issue where participants are influenced by experiencing one condition before another: can influence the IV and the DV
Idea
Any proposed relationship between variables, specific or otherwise
Uncertainty
In psychological research, uncertainty is how well (or not well) a sample parameter matches a population parameter
Discrete
A scale or a set of values are discrete if there are breaks or jumps in between them. Having group members labelled “person 1” and “person 2” uses discrete values as there is no “person 1½”
Contingency table
A table comparing expected and observed frequencies for a chi-square test
Type II error
False negative outcome; when the null hypothesis is not rejected, despite the population having an effect
Null hypothesis
The hypothesis that there is no effect in the population
Correlation coefficient
Effect size that measures the strength of a linear relationship on a normalized scale
Median
Measure of central tendency for Ordinal data, the middle value of a data set or halfway point between two central values
Non-parametric test
Statistical tests conducted on Ordinal or atypical data sets which don’t meet the requirements of parametric tests
Standard error
The standard deviation of the Sampling Distribution
Null hypothesis testing
Test used when looking for evidence to reject the null hypothesis
Likelihood
The relative chance that an event (like a sample) was caused by another event (like a specific population)
Variability
A term to describe the mount of differences between different people/animals/situations
Scatter plot
Type of graph with two continuous numeric variables plotted. Each data point is a single unconnected point in the graph
Opportunity sampling
Sampling strategy that uses any available group; no attempts to match a population or collect a random set of participants
Categories
The values of a categorical variable; also referred to as groups. Traits (e.g. blue eyes/brown eyes) or situations (before/after)
Path model
A model where variables are not as a simple split into predictors (IVs) and a response (DV) but are instead allowed to connect more freely
Mixed measures
Term used to describe an ANOVA where 1 or more variables are between-participants and 1 or more are within-participants
Likelihood function
A graph that shows the relative likelihood that a particular sample effect size came from a range of different population effect sizes
Residual
The difference between the expected value for an Interval DV and the actual value for one participant
AIC
Akaike Information Criterion. Value used to assess the fit of a model, typically by comparing models. Smaller is better
Natural effect size
An effect size measured in the same units as the DV
Type I error
False positive; the incorrect rejection of the null hypothesis
X-axis
Horizontal scale of a graph
Deviation
The difference between the value of a data point and the mean for that data set
Local mean
A theoretical concept where a set of values are divided into infinite small groups, and each group has its own mean, to generate a line of best fit
Logarithmic scale
A transformation that expands the amount of space given to small values and contracts the amount of space given to large values
Value
A specific description of a variable for one person or situation: e.g. ‘green’ for the variable eye colour, or ‘112’ for IQ score
Endogenous variable
A response variable, or dependent variable in a model
Interaction
A mechanism by which the effect of one IV on a DV depends on the value of another IV
Ordinal variable
A variable with ordered values, but no meaningful difference between values
Bar chart
Chart typically used to present frequencies of categorical data. Data illustrated using separated columns
Standard deviation
Measure of dispersion: based on the range of squared deviations from the mean. A small standard deviation indicates a small spread of values in a group
Parametric test
Standard null hypothesis statistical testing, typically between Interval and Categorical variables