If in a sample of 355 adult males, we have a mean total cholesterol level of 185 mg, with s = 16. What is the 95% confidence interval for mean total cholesterol level of all males?

Step-by-step explanation:

We want to determine a 95% confidence interval for the mean total cholesterol level of all males.

Number of sample, n = 355

Mean, u = 185 mg

Standard deviation, s = 16

For a confidence level of 95%, the corresponding z value is 1.96. This is determined from the normal distribution table.

We will apply the formula

Confidence interval

= mean + / - z * standard deviation/√n

It becomes

185 + / - 1.96 * 16/√355

= 185 + / - 1.96 * 0.849

= 185 + / - 1.66404

The lower end of the confidence interval is 185 - 1.66404 = 183.336

The upper end of the confidence interval is 185 + 1.66404 = 186.66

Therefore, with 95% confidence interval, the mean total cholesterol level of all males is between 183.336 mg and 186.66 mg