HP 48gII - Manual (Page 603)

Page 18-32
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
1
= 157.8 , x
2
= 160.0,
n
1
= 50, n
2
= 55. The populations standard deviations are s
1
= 13.2, s
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
1
and s
2
are the population standard
deviations. If these values actually represent the samples’ standard
deviations, you should enter the same values as before, but with the option
_pooled
selected. The results now become: