9. (6) Construct a confidence interval for Ma, the mean of the differences d for the population of paired data. Assume that the population of paired differences is
normally distributed.
Ten different families are tested for the number of gallons of water a day they use
before and after viewing a conservation video. Construct a 90% confidence interval
for the mean of the differences.
Before 33 33 38 33 35 35 40 40 40 31
After 34 28 25 28 35 33 31 28 35 33