Q1) Manufacturer of particular battery pack for laptop computer claims the battery pack can function for 8 hours, on the average, before having to be recharged. A random sample of 64 such battery packs was selected and tested. The mean and standard deviation were found to be 7.77 hours and 1 hour, respectively. Find a 90% confidence interval for the true time the battery pack can function before having to be recharged.

i) 7.985640 to 8.534278

ii) 8.0682 to 8.9318

iii) 7.564375 to 7.975625

iv) 7.486365 to 8.016559

2) A manufacturer claims that life span of its tires is 48,000 miles. You work for consumer protection agency and you are testing these tires. Suppose the life spans of tires are normally distributed. You choose 100 tires at random and test them. Mean life span is 47,840 miles. Suppose σ =700 .Compute parts (a) through (c)

a) Suppose the manufacturers claim is right, determine the probability the mean of sample is 47,840 miles or less ?

b) Using your answer from part a) what do you believe of the manufacturer claim

Claim is ............. because sample mean ........... be considered unusual since it ................Within ...............    of mean of the sample means

c) Would it be unusual to have individual tire with life span of 47,840 miles? Why or why not?

Suppose the manufacturers claim is true, because 47,840 ......... within ................ Of the mean for an individual tire.