Ch.5 Normal Distributions

Density curve

describes the overall pattern for a continuous distribution

- always located above the X-axis

-area under the curve is exactly 1

-the median divides the area under the curve in half

Normal distribution curve

-continuous -symmetric -bell shaped - unimodal -doesn't touch the x-axis -total area under the curve is equal to 1

68% rule

For a normal distribution, 68% of the observations lie within 1 standard deviation of the mean

95% rule

for a normal distribution - 95% of observations lie within 2 standard deviations of the mean

99% rule

for a normal distribution - 99% of distributions lie within 3 standard deviations of the mean