Question

The cholesterol levels of a random sample of 250 men are measured. The sample mean is 182 and the sample standard deviation is 32.

a. Give the value of the point estimate of the mean cholesterol level for men in interval notation.
b. Give the value of the standard error of the mean cholesterol level for men.
c. Give the value of the margin of error of the mean cholesterol level for men for a 95% confidence interval.
d. Give the value of the point estimate of the mean cholesterol level for men in interval notation.

Answer 1

182

2.0239

3.97

(178, 186)

Explanation:

Given :

Sample mean, n = 250

Sample mean, xbar = 182

Sample standard deviation, s = 32

Point estimate for the mean ;

According to the central limit theorem ; for n > 30, the sample mean equal to the population mean.

Hence, point estimate of mean cholesterol level for men is 182

B.) The standard error = s/√n

s= 32 ; n = 250

Standard error = 32/√250 = 2.0239

C.) Margin of error :

TCritical * standard error

TCritical at 95% ; df =250 -1 = 249 = 1.96

1.969 * 2.0239 = 3.966 = 3.97

D.) The confidence interval :

Point estimate ± margin of error

182 ± 3.97

182 - 3.97 = 178.03

182 + 3.97 = 185.97

(178, 186)