Question

Consider an x distribution with standard deviation σ = 28. (For each answer, enter an exact number.)

(a) If specifications for a research project require the standard error of the corresponding x bar distribution to be 2, how large does the sample size need to be? n =

(b) If specifications for a research project require the standard error of the corresponding x bar distribution to be 1, how large does the sample size need to be? n =

Answer 1

Standard error = Standard deviation / sqrt (n)

a)

2 = 28 / sqrt(n)

Sqrt (n) = 28 / 2

sqrt(n) = 14

n = 196

b)

1 = 28 / sqrt(n)

Sqrt (n) = 28 / 1

sqrt(n) = 28

n = 784