A distribution of values is normal with a mean of 6.7 and a standard deviation of 21.8. Find P71, which is the score separating the bottom 71% from the top 29%.

Question

I am super confused on how to solve this problem... any help?

Answer 1

One thing that might be a little confusing is that as the problem is written, some of the values in this distribution are negative.

One needs a calculator or computer statistics package or access to a standard normal distribution table.

Using a TI-84 or TI-83 calculator, use the second-DISTR function InvNorm (which is Inverse Normal) with

area = .71 (71% of values are less than this value)

µ = 6.7 (mean is 6.7)

σ = 21.8 (standard deviation is 21.8)

The answer is 18.76