1. ## 99% confidence interval

I have worked on this problem for awhile trying it different ways -

A random sample of 250 students at a university finds that these students take a mean of 15 credit
hours per quarter with a standard deviation of 1.6 credit hours. Estimate the mean credit hours
taken by a student each quarter using a 99% confidence interval.
Mean: 15
Standard deviation σ: 1.6 # of Samples : 250 Confidence interval %: 99%
Standard deviation σx of the set of sample mean = σ / √n
σx = 0.101

99% of the sample means should be within 2.576 standard deviations of the population mean.
Therefore,
Confidence interval = Sample Mean ± 2.576 × σx
= 15 ± 2.576 × 0.101
= 15 ± 0.261

I had other choices such as 15 + - .013; 15 + - .016 and 15 + - 206 but with my calculations I ended up with my solution of 15 + - 0.261

Does anyone think I did this correctly or did I make a mistake somewhere...

Statistics is a bit challenging for me and any input would be greatly appreciated.

Thanks and have a great holiday.

2. Your answer is correct. The given solutions are wrong. Well done! :-)

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