Question

Give a 99.9% confidence interval, for μ1−μ2μ1-μ2 given the following information.
n1=50n1=50, ¯x1=2.32x¯1=2.32, s1=0.68s1=0.68
n2=35n2=35, ¯x2=1.98x¯2=1.98, s2=0.38s2=0.38

For degrees of freedom, use the smaller of
(n1−1)(n1-1) and (n2−1)(n2-1)

tα2tα2 = tinv(α, df)

SE = sqrt((s1s1)^2 / n1n1 + (s2s2)^2 / n2n2)

E = tα2tα2 * SE

CI = (¯x1−¯x2)±E(x¯1-x¯2)±E

Rounded both solutions to 2 decimal places.

Can I have this done in excel please?

Answer 1

Given:

n1 = 50, n2 = 35, = 2.32, = 1.98, S1 = 0.68, S2 = 0.38, = 0.001

Degrees of freedom =

Critical value:

..........................Using t table

Standard Error (SE):

Margin of error (ME) = Critical value * SE

Margin of error (ME) = 3.4180 * 0.12 = 0.3953

99.9% Confidence interval:

(2.32 - 1.98) - 0.3953 to   (2.32 - 1.98) + 0.3953

(-0.06 to 0.74)

We are 99.9% Confident that Population mean difference is lies between this interval.