Two Sample Stuff--Help!
Message posted by Michelle (via 140.209.38.156) on November 19, 2001 at 10:46 AM (ET)

I think this should be done with Minitab, but I'm not sure:
"At a large industrial plant, employees were classified according to age and given a leadership exam. The data are the scores on the exam:
Under 35: 9 46 25 30 17 20 17 20 37 25 26 23 20 17 11 36 30 12 32 44 24 20 16 8 21 37 31
Over 35: 43 23 13 23 21 42 34 14 15 38 30 14 45 19 26 38 29 9 50 41 13 15 16 48 32 7 9 28 30
Evaluate the claim that the mean score for the over-35 group exceeds the mean score for the under-35 group."

If anyone could give me insight to this I'd really appreciate it! Thank you so much!

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Re: Two Sample Stuff--Help!
Message posted by Mark Waters (via 128.243.220.25) on November 19, 2001 at 12:14 PM (ET)

You have two samples, and you want to find out if the mean of each is significantly different from one another. My advice is to do a two-sample t-test like this:

MTB > TwoSample C1 C2.

You will get a print out that gives you basic stats of each sample, plus this:

95% CI for difference: (-8.32, 4.01)
T-Test of difference = 0 (vs not =): T-Value = -0.70 P-Value = 0.486 DF = 52

The important stuff for your purpose is the P-value, which shows that the null hypothesis cannot be rejected (make sure you state the null hypothesis in you work) at the 5% level. Note also that the 95% confidence interval spans zero - which is a sure sign of insignificance, because it is basically saying that the difference between the two samples could be zero, which by definition means there is no significant difference.

Hope this helps. Sorry to be patronising if you knew some of this already ;-)