Assume 18 power wrenches used on an assembly line of a manufacturing company are randomly selected. The sample standard deviation of the amounts of torque applied is 0.62 foot-pound.

a. (10 points)

Test the claim that the population standard deviation of the amounts of torque applied is less than 0.65 foot-pound using = 0.10.

H₀ :

H₁ :

Critical number(s) =

Round the same as the critical number(s). Test statistic =

H₀

There sufficient evidence to the claim that the population standard deviation of the amounts of torque applied is less than 0.65 foot-pound.

b. Find a 95% confidence interval estimating the population standard deviation of the the amounts of torque applied. (10 points)

Values from the appropriate table =

Round to two decimal places. Include units. Confidence interval =