Question

"You measure 34 dogs' weights, and find they have a mean weight of 67 ounces. Assume the population standard deviation is 13.5 ounces. Based on this, construct a 95% confidence interval for the true population mean dog weight."

Answer 1

The 95% confidence interval for the true population mean dog weight is between 62.46 ounces and 71.54 ounces.

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 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*(13.5)/(√(34)) = 4.54`

The lower end of the interval is the sample mean subtracted by M. So it is 67 - 4.54 = 62.46 ounches.

The upper end of the interval is the sample mean added to M. So it is 67 + 4.54 = 71.54 ounces.

The 95% confidence interval for the true population mean dog weight is between 62.46 ounces and 71.54 ounces.