HP 39gs Master Guide

Confidence interval: T-Int 1- µ
In the previous example we found that the evidence of our sample indicated that the mean number of matches
in the boxes was not 50. Suppose we now want to know, at the 95% confidence level, within what range of
values the true population mean lies.
the method of Conf
Interval.
The type of interval is converted to the equivalent type of T-INT: 1
µ .
Change back to the
SYMB view and
In the
NUM SETUP view use the import facility as before to import the
values from our sample data. The default confidence level is 99% so you
will need to change that to 0.95.
Changing to the
NUM view gives the minimum and maximum values for
the population mean of 50.16 to 52.44 at a 95% confidence level.
As before, a more visual display can be seen in the
PLOT view.
Thus the sample data indicates in our two examples that:
• we can be confident the average number of matches is not 50
with less than a 5% chance of being wrong, and
• we can conclude, with a confidence of 95%, that the true
average number of matches is between 50.16 and 52.44.
143

HP 39gs Specifications

General

Type	Scientific
Form factor	Pocket
Product color	Gray
Internal memory	0.256 MB

Weight and Dimensions

Weight	249 g
Dimensions (WxDxH)	187 x 94 x 31 mm