Question

A sample of 18 randomly selected women is obtainedand the blood platelet count of each subject is measured. The mean is 253.9 and the standard deviation is 63.6. What is the margin of error (round to the nearest tenth)?

Answer 1

Margin of error = E = 40

Explanation:

Assuming 99% confidence level

Given that x = 253.9

s.d = 63.6

n = 18

Degrees of freedom = df = n - 1 = 18 - 1 = 17

At 99% confidence level the t is, α = 1 - 99% = 1 - 0.99 = 0.01

α/2 = 0.01 / 2 = 0.005

t α/2,df = t,0.005 = = 2.680 (using student t table)

Margin of error = E = t α/2,df * (s.d/√n)

Margin of error = 2.680*63.6/√18

Margin of error = 2.680*63.6/4.242641

Margin of error = 2.680*14.99066265564303

Margin of error = 40.17

Margin of error = E = 40