Question

Two samples are taken with the following sample means, sizes, and standard deviations ¯ x1 x¯1 = 31 ¯ x2 x¯2 = 28 n1 n1 = 70 n2 n2 = 46 s1 s1 = 4 s2 s2 = 2

We want to estimate the difference in population means using a 89% confidence level. What distribution does this require? t, df = 108 z NOTE: The more accurate df formula, used above, is: df= ( s 2 1 n1 + s 2 2 n2 )2 1 n1−1 ⋅( s 2 1 n1 )2+ 1 n2−1 ⋅( s 2 2 n2 )2 df=(s12n1+s22n2)21n1-1⋅(s12n1)2+1n2-1⋅(s22n2)2

What is α?

What is the critical value for the confidence interval?

NOTE: Use the df given in the question above, The 89% confidence interval is: 2.09<μ1−μ2<3.91 2.09<μ1-μ2<3.91

Does this interval include 0?

What does that decision mean?   It excludes 0? The two population means are different. It does include 0? The two population means seem to be equal?

Answer 1