Download NORMAL DISTRIBUTION-2 A normal distribution is a very important

NORMAL DISTRIBUTION-2
A normal distribution is a very important statistical data distribution pattern occurring in many natural
phenomena, such as height, blood pressure, lengths of objects produced by machines, etc. Certain data,
when graphed as a histogram (data on the horizontal axis, amount of data on the vertical axis), creates a bellshaped curve known as a normal curve, or normal distribution.
Normal distributions are symmetrical with a single central peak at the mean (average) of the data. The
shape of the curve is described as bell-shaped with the graph falling off evenly on either side of the mean.
Fifty percent of the distribution lies to the left of the mean and fifty percent lies to the right of the mean.
The spread of a normal distribution is controlled by the standard deviation,
deviation the more concentrated the data.
. The smaller the standard
The mean and the median are the same in a normal distribution.
Chart prepared by the NY State Education Department
Reading from the chart, we see that approximately 19.1% of normally distributed data is located between the
mean (the peak) and 0.5 standard deviations to the right (or left) of the mean.
(The percentages are represented by the area under the curve.)
If you add percentages, you will see that approximately:
• 68% of the distribution lies within one standard deviation of the mean.
• 95% of the distribution lies within two standard deviations of the mean.
• 99.7% of the distribution lies within three standard deviations of the mean.