- 23/23.5 Final Exam-Page 7 of 9 (10 points) A random sample of 14 months at the O'Sullivan household showed the family received an average of x=72 solicitation phone calls each month. The sample standard deviation was s=27. Find a 95% confidence interval for the population mean number of solicitation calls this family receives each month. Assume x has a distribution tl Answer: The confidence interval is