The command pnorm can be used to compute the proportion of a
standard normal distribution that is below 0.5:
One way to compute the proportion of a normal distribution with mean
76 and standard deviation 10 that is below 80 is to compute the z
score
z = (80 - 76)/10 = 0.4 and then use pnorm to find the
proportion of a standard normal distribution that is below z = 0.4:
An alternative is to give the pnorm the mean and standard
deviation to use as additional arguments:
Percentiles of the standard normal distribution are computed with
qnorm. The 80th percentile is computed by
The 80th percentile of a normal distribution with mean 76 and standard
deviation 10 can be found by computing the z score, the 80th
percentile of the standard normal distribution, and converting the z
score back to the original units:
Again, an alternative is to give qnorm the mean and standard
deviation to use:
Try some examples of your own in the work area below.
Work Area
Enter your own commands here; then click the Submit button.
