within one standard deviation of the mean, about 95% are within two standard deviations, and about
99.7% are within three standard deviationsEstimate —sample value used to approximate a value of a parameter
Event —in probability, a subset of a sample space; a set of one or more simple outcomes
Expected value —mean value of a discrete random variable
Experiment —study in which a researcher measures the responses to a treatment variable, or variables,
imposed and controlled by the researcher
Experimental units —individuals on which experiments are conducted
Explanatory variable —explains changes in response variable; treatment variable; independent variable
Extrapolation —predictions about the value of a variable based on the value of another variable outside
the range of measured values
First quartile —25th percentile
Five-number summary —for a dataset, [minimum value, Q1, median, Q3, maximum value]
Geometric setting —independent observations, each of which succeeds or fails with the same
probability p ; number of trials needed until first success is variable of interest
Histogram —graph in which the frequencies of numerical data are displayed with bars; analogous to a
bar graph for categorical data
Homogeneity of proportions —chi-square hypothesis in which proportions of a categorical variable are
tested for homogeneity across two or more populations
Independent events —knowing one event occurs does not change the probability that the other occurs; P
(A) = P (A|B)
Independent variable —see explanatory variable
Inferential statistics —use of sample data to make inferences about populations
Influential observation —observation, usually in the x direction, whose removal would have a marked
impact on the slope of the regression line
Interpolation —predictions about the value of a variable based on the value of another variable within
the range of measured values
Interquartile range —value of the third quartile minus the value of the first quartile; contains middle
50% of the data
Least-squares regression line —of all possible lines, the line that minimizes the sum of squared errors
(residuals) from the line
Line of best fit —see least-squares regression line
Lurking variable —one that has an effect on the outcomes of the study but whose influence was not part
of the investigation
Margin of error —measure of uncertainty in the estimate of a parameter; (critical value) · (standard
error)
Marginal totals —row and column totals in a two-way table
Matched pairs —experimental units paired by a researcher based on some common characteristic or
characteristic
Matched pairs design —experimental design that utilizes each pair as a block; one unit receives one