The Professor's Response

Professor,
I need help with question 18 from section 9.4. Could you please show how you get the test stat of 11.44, I get something different.
Thank You.

  See the professor's answer below.

Professor McGukian

Hi Peggy,

I can create a video for this later, but for now, let me just explain here:

Because we assume equal variances for this problem, we first need to calculate Sp²

Sp² = [(n1-1)*S1² + (n2-1)*S2²]/(n1 + n2 - 2)

(27*4.51² + 28*3.98²)/(28+29-2) = 18.04934364 = Sp²

Then our test stat formula for this problem would be:

t = (Xbar1 - Xbar2) / SqrRoot(Sp²/n1 + Sp²/n2) = (38.28 - 25.4) / SqrRoot(18.04934/28 + 18.04934/29) = 11.443

Note: the denominator part of the test stat (the part under the squareroot) should be 1.125615643. Use that to check your calculation.

Hope that helps,

Professor

 

Professor McGukian

Hi Peggy,

Here is a video explanation of how to work out the test statistic:

 

 

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