Determining sample size using standard deviation

Reference no: EM1321443

Q1) Cell phone manufacturer claims that its phone will last for more than 8 hours of continuous talk time when battery is fully charged. To test this claim a sample of n = 18 phones were tested. Results showed sample mean of 8.2 hours and sample standard deviation of 0.4 hours. Carry out hypothesis test using 0.05 level of significance and find out whether or not company's claim is supported.

Q2) Major tire manufacturer wants to evaluate mean tread life in miles for one of their tires. They want to develop confidence interval estimate that would have maximum sampling error of 500 miles with 90 percent confidence. Pilot sample of n = 50 tires illustrated sample standard deviation equal to 4,000 miles. Based on this information, required sample size is:

a) 124.

b) 246.

c)174.

d) 196.

Reference no: EM1321443

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