Video Transcript
For a normally distributed data
set, approximately what percentage of data points will lie within one standard
deviation of the mean?
The graph of a normal distribution
is a bell-shaped curve, and it’s completely symmetrical about the mean. The area beneath the curve is one,
or 100 percent. And we model our data by
considering its distance from the mean in terms of the standard deviation 𝜎. And this is sometimes called the
68-95-99.7 rule. It tells us that approximately 68
percent of data points will lie within one standard deviation of the mean. And then approximately 95 percent
of data points lie within two standard deviations of the mean. And finally, approximately 99.7
percent of data points lie within three standard deviations of the mean.
Using the 68-95-99.7 rule, we can
say that for one standard deviation in a normally distributed data set, 68 percent
of the data points will lie within one standard deviation of that mean.
