1. In a random sample of 44 downloadable books from a website, the mean cost is...

1. In a random sample of 44 downloadable books from a website, the mean cost is $8.58 with a standard deviation of $2.09.

Which interval is the 95% confidence interval for the mean cost of all the downloadable books on the website?

($7.96, $9.20)

($7.77, $9.35)

($8.39, $8.77)

($8.26, $8.90)

2.) In a random sample of 80 students in first grade, the mean hours of sleep per night was 9.4 with a standard deviation of 0.41. In a random sample of 50 students in 12th grade, the mean hours of sleep per night was 7.5 with a standard deviation of 0.52.

Which interval is a 99% confidence interval for the difference between the mean hours of sleep?

(1.75 h, 2.05 h)

(1.89 h, 1.91 h)

(1.43 h, 2.37 h)

(1.68 h, 2.12 h)

Solutions

Expert Solution

The solution is done showing all steps with calculation and necessary formulas. For better understanding a value table is also attached. Hope you can understand.

z-table -

orchestra answered 1 year ago

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