Q1) Do middle-aged male executives have different average blood pressure than general population? National Center for Health Statistics reports that mean systolic pressure for males ages 35 to 44 is 128 and standard deviation of this population is 15. Medical director of company looks at medical records of 72 company executives in this age group and determines that mean systolic blood pressure in this sample is 126.07. Is this evidence that executive blood pressures vary from national average? Use 5% level of significance.

Q2) A sample of 25 different payroll departments determined that employees worked average of 310.3 days year with standard deviation of 23.8 days.  Determine the 90% confidence interval for average days worked by employees in all payroll departments?

a) 301.0 < µ < 319.6

b) 298.0 < µ < 322.6

c) 302.4 < µ < 318.2

d. 314.1 < µ < 316.8

Q3) A previous study of nickels showed that the standard deviation of the weight of nickels is 150 milligrams.  How many nickels does a coin counter manufacturer need to weigh so that she can be 98% confident that her sample mean is within 25 milligrams of true average weight of nickel?

a) 36

b) 195

c) 239

d) 139

Q4) Food snack manufacturer samples 15 bags of pretzels off assembly line and weighed their contents.  If sample mean is 10.0 and sample standard deviation is 0.15, determine 95% confidence interval estimate for the true mean.

a) (9.96, 10.04)

b) (9.68, 10.32)

c) (9.97, 10.80)

d) (9.92, 10.08)