AP Statistics 2.2 - Density Curves and Normal Distributions

density curve

a curve that 1) Is always on or above the horizontal axis 2) Has area exactly 1 underneath it

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.

µ (the Greek letter mu)

mean of a density curve

σ (the Greek letter sigma)

standard deviation of a density curve

Normal curves

symmetric, bell-shaped curves; describe Normal distributions.

Normal distribution

described by a symmetric, single-peaked, bell-shaped density curve called a Normal curve.

68-95-99.7 rule

In a Normal distribution with mean µ and standard deviation σ:
Approximately 68% of the observations fall within σ of the mean µ.
Approximately 95% of the observations fall within 2σ of the mean µ.
Approximately 99.7% of the observations fall within 3σ of the mean µ.

standard Normal distribution

the Normal distribution with mean 0 and standard deviation 1.