Question

5. A study found that the average time it took a person to find their dream home was 5.9 months. If a sample of

36 people were surveyed, find the 95% confidence interval of the mean. Assume the standard deviation of
the population is 0.8 month.

Answer 1

The 95% confidence interval of the mean time it took a person to find their dream home is between 5.64 months and 6.16 months.

Explanation:

We have that to find our
`\alpha` level, that is the subtraction of 1 by the confidence interval divided by 2. So:

`\alpha = (1-0.95)/(2) = 0.025`

Now, we have to find z in the Ztable as such z has a pvalue of
`1-\alpha`.

So it is z with a pvalue of
`1-0.025 = 0.975`, so
`z = 1.96`

Now, find the margin of error M as such

`M = z*(\sigma)/(√(n))`

In which
`\sigma` is the standard deviation of the population and n is the size of the sample.

`M = 1.96(0.8)/(√(36)) = 0.26`

The lower end of the interval is the sample mean subtracted by M. So it is 5.9 - 0.26 = 5.64 months

The upper end of the interval is the sample mean added to M. So it is 5.9 + 0.26 = 6.16 months.

The 95% confidence interval of the mean time it took a person to find their dream home is between 5.64 months and 6.16 months.