What is the mean and standard deviation

Reference no: EM13986666

1) A manufacturer of cell phones batteries wants to estimate the useful life of its battery (in thousands of hours). The estimate needs to be within 0.10 (100 hours). Assuming a 95% level of confidence and a standard deviation of the useful life of the battery is 0.90 (900 hours). Determine the sample size. [Hint: First, determine the maximum allowable error from the above information and then apply the formula for estimating the sample size]

2) Historically, the proportion of adults over the age of 24 who smoke has been 0.30. A more recent sample of 500 adults revealed only 25% of those sampled smoked. Develop a 98% confidence interval for the proportion of adults who currently smoke. Is this confidence interval less than the historic average? [Hint: Is the population standard deviation known?]

3) A local radio station provides morning drive-time news. They also encourage listeners to weigh in on topics. This morning the question was: how many hours do children under 12 years of age watch TV per day. Five callers responded that their children watched the following number of hours of TV last night:

Caller	TV Hours
1	3.0
2	3.5
3	4.0
4	4.5
5	3.0

a) What is the mean?

b) What is the standard deviation? [Remember: this is a small sample.)

c) What is the range of hours of TV watched?

Reference no: EM13986666

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