Question

A random sample of 40 videos posted to YouTube was selected. A month later, the number of times that each had been viewed was tabulated. The mean number of viewings was 121 with a sample standard deviation of 500 . Find the upper bound of the 99% confidence interval for the mean number of times videos posted to YouTube have been viewed in the first month.

Round to the nearest integer. Write only a number as your answer. Do not write any units.

Answer 1

Solution :

Given that,

= 121

s = 500

n = 40

Degrees of freedom = df = n - 1 = 40 - 1 = 39

At 99% confidence level the t is ,

= 1 - 99% = 1 - 0.99 = 0.01

t ,df = t0.01,39 = 2.426

Margin of error = E = t,df * (s /n)

= 2.426 * (500 / 40)

= 191.79

The 99% confidence interval estimate of the population mean is,

- E < < + E

121 - 191.79 < < 121 + 191.79

-70.79 < < 312.79

Upper bound = 313