Question

If σ = 12, find the sample size to estimate the mean with an error of ±4 and 95 percent confidence (rounded to the next higher integer).

Multiple Choice

• 35

• 75

• 58

• 113

Answer 1

Solution :

Given that,

standard deviation = = 12

margin of error = E = 4

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.960

Sample size = n = ((Z/2 * ) / E)2

= ((1.960 * 12) / 4)2

= 35

Sample size = 35

Option 35 is correct.