ap stats chapter 2

density curve

describes overall pattern of a distribution

median

point that divides the area under the curve in half

mean

the balance point at which the curve would (hypothetically) balance

normal (bell) curve

symmetric, bell-shaped, single-peaked density curve

on a normal curve the mean controls…

the center

on a normal curve the standard deviation controls…

the spread

68-95-99.7 rule

(only works with normal distributions)

~68% of observations fall within 1σ of µ

~95% of observations fall within 2σ of µ

~99.7% of observations fall within 3σ of µ

measures of center

mean and median

affected by + - × ÷

points of location

mode, quartiles, percentiles

affected by + - × ÷

measures of spread

range, interquartile, standard deviation

affected by × ÷

shape of distribution

never affected by transformations

standardized values

z-score

never affected by transformations

cumulative relative frequency

a graph where plotted points correspond to a percentile of a given value in a distribution of quantitative data