AP Stat Vocabulary Unit 2

z-score

tells us how many standard deviations from the mean an observations falls, and in what direction (value - mean / SD)

percentile

the value with p% of observations LESS THAN OR EQUAL to it

Cumulative relative frequency graph

plots a point corresponding to the percentile of a given value in a distribution of quantitative data

Transforming

converts the original observations from the original units of measurements to another scale

Density Curve

the area under this curve and above any interval of values on the horizontal axis estimates the proportion of all observations that fall in that interval

Mean of a Density Curve

the point at which the curve would balance if made of solid material

Median of a Density Curve

the equal-areas point, the point that divides the area under the curve in half

Normal distribution

described by a symmetric, single-peaked, bell-shaped density curve called a NORMAL CURVE

Empirical Rule (68-95-99.7)

in a normal distribution, ~68% of observations fall within 1 SD of the mean, ~95% of observations fall within 2 SD of the mean, and ~99.7% of observations fall within 3 SD of the mean

Sample Normal Distribution

the normal distribution with mean 0 and SD 1 —- use when referring to z-scores

Standard Normal distribution

the normal distribution with mean 0 and SD 1 (use when referring to z-scores)