Customer database A large philanthropic organization keeps records on the people who have contributed. In addition to keeping records of past giving, the organization buys demographic data on neighborhoods from the U.S. Census Bureau.

Eighteen of these variables concern ethnicity. Here are a histogram and summary statistics for the percentage of whites in the neighborhoods of 500 donors:

a) Which is a better summary of the percentage of white residents in the neighborhoods, the mean or the median?
Explain.

b) Which is a better summary of the spread, the IQR or the standard deviation? Explain.

c) From a Normal model, about what percentage of neighborhoods should have a percent white within one standard deviation of the mean?

d) What percentage of neighborhoods actually have a percent white within one standard deviation of the mean?

e) Explain the discrepancy between parts c and d.