HP F2226A - 48GII Graphic Calculator User Manual page 603

The figure shows the Student's t pdf for ν = 50 – 1 = 49 degrees of freedom.
Example 6 -- Determine the 99% confidence interval for the difference in
means of two populations given the sample data:x = 157.8 ,x = 160.0,
1 2
n = 50, n = 55. The populations standard deviations are s = 13.2, s =
1 2 1 2
24.5.
Press ‚Ù—@@@OK@@@ to access the confidence interval feature in the
calculator. Press —@@@OK@@@ to select option 6. T-INT: µ1−µ2.. Enter the
following values:
hen done, press @@@OK@@@. The results, as text and graph, are shown below:
These results assume that the values s and s are the population standard
1 2
deviations. If these values actually represent the samples' standard
deviations, you should enter the same values as before, but with the option
selected. The results now become:
_pooled
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