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predictor variable
a variable which is believed to predict another variable

covariance
describes the linear association between two quantitative variables

scatterplot
graphical representation of the association between two quantitative variables

Pearson Correlation
 a measure of the association between two variables which is defined on a scale from 1 to 1, with 1 being a perfect positive relationship and a 1 being a perfect negative relationship


coefficient of determination
measure of the association between two variables, equal to the squared Pearson correlation. Describes the proportion of variance in one variable that is linearly associated with the other variable

linear regression model
can be used to descrive the relation between x and y in a random sample of participants

randomx model
linear regression model in which each person in a random sample is assigned a pair of x and y scores, where the x values observed in the sample will not be known in advance.

fixedx model
linear regression model in which the values of x are predetermined by the researcher

slope
describes the change in the predicted y score associated with any 1point increase in x; _{1}

least squares estimate
the unique values that minimize the sum of all squared residual scores ( )

centering predictor variable
subtracting from each x score so that the predictor variable's mean will equal 0 and

Fisher transformation
 used to transform a Pearson correlation coefficient to obtain a confidence interval

dummy coded predictor variable
setting x _{i}=1 for every participant in the first group and x _{i}=0 for every participant in the second group; in this model,

pointbiserial correlation
describes the strength of the relation between a quantitative response variable and a dichotomous predictor variable

reliability
the squared Pearson correlation between the true scorfes and the measured scores

measurement error
the difference between the true score and the observed measurement of the true score

alternative form reliability
the Pearson correlation between two measurements of a randomly selected participant's particular attribute

testretest relibaility
Pearson correlation between two occasions of the same form for a randomly selected participant

interrater reliability
the Pearson correlation between two measurements of a randomly selected participant given by two different raters

validity
the degree to which a measurement assesses the attribute it claims to measure

criterion validity
obtained by assessing the magnitude of a correlation (Pearson or pointbiserial) between the measurement in question and some objective behavioral criterion or performance on a specific task

construct validity
obtained by assessing the magnitude of a correlation between the measurement in question (y) and the measurements of several other psychological measurements

linearity assumption
the assumption that the relation between y and x is linear

errror normality assumption
the assumption that the prediction errors have an approximate normal distribution in the study population

bivariate normality assumption
in randomx models, the assumption that x and y have an approximate bivariate normaldistribution

outlier
unusually small or large x or y scores

data transformations
A logarithmic, square root, or reciprocal transformation of an x or y score to normalize the scores

