Q1) Length of human pregnancies is approximately normally distributed with mean µ= 226 days and standard deviation σ = 16 days.  Dr. Margaret Miller gets simple random sample of 10 of her patients and obtains following results:

i) Use the data to compute a point estimate for the population mean gestation period.

ii) Create a 90% confidence interval for mean gestation period for all of Dr. Miller's patients. Interpret this interval.

iii) Do Dr. Miller's patients have a mean gestation period different from 266 days?

iv) Why or why not?

Q2) Insurance Institute for Highway Safety routinely conducts crash tests on vehicles to find out the cost of repairs.  In 4 crashes of a Chevy Cavalier at 5 mph, institute found the cost of repairs to be= $225, $462, $729, and $753.  Treat these data as simple random sample of four crashes, and reply the following questions, assuming that σ = $220

i) Use data to calculate a point estimate for population mean cost of repairs on a Chevy Cavalier.

ii) Create a 95% confidence interval for mean cost of repairs. Interpret this interval.

iii) Assume we are in planning stages of this investigation.  We require to find out how many observations must be in our sample to restrict our margin of error to $150

Find the required sample size.