A homeowner was interested in the size of homes in Buncombe County. He went door to door in his subdivision and recorded the size (in square feet) of the 30 homes in that subdivision. From this data he calculated a 95% confidence interval for the averarage size of these homes to be 1900 ±11. This interval is not appropriate because
Select one:
a. the size of homes is likely to be skewed and confidence intervals are based on the normal distribution.
b. this is not a random sample.
c. a sample size of 30 is not large enough to produce 95% confidence.
d. both a and b.