Question

3.For a 95% confidence level, with a standard deviation equal to 25 and a sampling error of 5, calculate the sample size

a.99.96

b.61.47

c.96.04

d.75.00

Answer 1

Solution:

confidence level = c= 95%

standard deviation = = 25

Margin of error = E = 5

Sample size n is:

We need to find z_c value for c=95% confidence level.

Find Area = ( 1 + c ) / 2 = ( 1 + 0.95) /2 = 1.95 / 2 = 0.9750

Look in z table for Area = 0.9750 or its closest area and find z value.

Area = 0.9750 corresponds to 1.9 and 0.06 , thus z critical value = 1.96

That is : Z_c = 1.96

Thus

thus correct answer is: c.96.04