Two or more variables are confounded if their effects cannot be separated because they vary together
confound variables
Tables displaying correlation coefficients that describe the relationships among multiple variables
correlation matrices
When variables differ together; that is, when one score changes, the other score also changes in a predictable or consistent way
covariance
Forms of regression that can explain curves in the data rather than straight lines
curvilinear models
A relationship in which a line through the middle of the points in a scatter plot will be curved rather than straight
curvilinear relationship
variables are related but move in opposite directions when they change: as one variable goes up, the other variable goes down
inverse relationship
a scatter plot of the points falls on a straight line
linear relationship
How strong or how consistent the relationship between variables is
magnitude
as the value of one variable increases, the other decreases
negative relationship
the hypothetical line drawn through points on a scatter plot has no slope; in other words, values of X are not associated with the values of Y
no relationship
An atypical, infrequent observation; a value that has an extreme deviation from the center of the distribution
outlier
smaller values of X are associated with smaller values of Y
positive relationship
Failure to capture the full range of a variable’s potential scores
range restriction
A statistic that expresses the relationship between two variables on a scale from 1 to –1
Spearman’s rho
