Question

Suppose that a certain website claims that it averages 4.7 hours of downtime per month. (Downtime is time that the site is not available.) 

In a random sample of 17 months, the average downtime was 4.9 hours per month, with a standard deviation of 0.5 hours per month. What is the z-value rounded to the nearest hundredth?  Is there enough evidence to reject the claim?​

Answer 1

The z-value rounded to the nearest hundredth is -1.64

There is no enough evidence to reject the claim.

Explanation:

A certain website claims that it averages 4.7 hours of downtime per month.

No. of samples = n = 17

Mean =
`\mu = 4.9`

Standard deviation =
`\sigma = 0.5`

Formula:
`Z=(x-\mu)/((\sigma)/(√(n)))`

`Z=(4.7-4.9)/((0.5)/(√(17)))`

Z =−1.64

Z critical at 90% is 1.65

Since Z calculated < Z critical

So, there is no enough evidence to reject the claim.