Glossary Portney & Watkins Flashcards
regression line
The straight line that is drawn on a scatter plot for bivariate data from the regression equation, summarizing the relationship between variables.
sampling error
The difference between an observed statistic from a sample and the population parameter.
analysis of covariance (ANCOVA)
Statistical procedure used to compare two or more treatment groups while controlling for the effect of one or more confounding variables (called covariates).
positive predictive value
Estimate of the likelihood that a person who tests positive actually has the disease.
curvilinear relationship
The relationship between two variables that does not follow a linear proportional relationship.
phi coefficient
A nonparametric correlation statistic for estimating the relationship between two dichotomous variables.
Type II error
An incorrect decision to accept the null hypothesis, concluding that no relationship exists when in fact it does.
z-score
The number of standard deviations that a given value is above or below the mean of the distribution; also called a standardized score.
stratification
The grouping of individuals in a population into homogeneous groups on some characteristic prior to sampling.
sXhat
standard error of the mean
The standard deviation of ta distribution of sample means; an estimate of the population standard deviation
audit trail
Comprehensive process of documenting interpretation of qualitative data.
epidemiology
Study of the distribution of disease in relation to person, place and time, and measures of risk associated with exposures to disease.
nondirectional hypothesis
A research hypothesis (or alternative hypothesis) that does not indicate the expected direction of the relationship between variables.
target population
The larger population to which results of a study will be generalized.
grand mean
The mean of all scores across groups in an analysis of variance.
longitudinal study
A study designed to collect data over time, usually for the purpose of describing developmental changes in a particular group.
Newman-Keuls (NK) multiple comparison test
Amultiple comparison procedure, used following a significant analysis of variance. Also called the Student-Newman-Keuls (SNK) test.
nominal scale
Level of measurement for classification variables; assignment of “values” based on mutually exclusive and exhaustive categories with no inherent rank order.
Q-sort
An analytic technique used to characterize attitudes, opinions, or judgments of individuals through a process of comparative rank ordering.
treatment threshold
In clinical decision making, the point at which a decision is reached to treat the patient without first performing a diagnostic test.
Wilcoxon signed-ranks test (T)
A nonparametric statistical procedure, comparing two correlated samples (repeated measures); analogous to the paired t-test.
z distribution
The standardized normal distribution, with a mean of 0 and a standard deviation of 1.
Bayes’ theorem
The calculation of the probability of one event based on the probability of another event; used to estimate posterior (posttest) probabilities based on prior (pretest) probabilities of a diagnostic outcome.
degrees of freedom (df)
Statistical concept indicating the number of values within a distribution ntat are free to vary, given restrictions on the data set; usualy n-1. For analysis of variance, dfe = error degrees of freedom; dfb = between groupus degrees of freedom; dft = total degrees of freedom




