Microsoft Office Tutorials and References
In Depth Information
Next, name the range of data from A6:A30 as: miles
D7:
Use Excel to find the sample size
D10:
Use Excel to find the mean
D13:
Use Excel to find the STDEV
D16:
Use Excel to find the s.e.
Now, you need to find the lower limit and the upper limit of the 95 % confi-
dence interval for this study.
We will use Excel’s TINV function to do this. We will assume that you want to
be 95 % confident of your results.
F21:
=D10-TINV(1-.95,24)*D16
Note that this TINV formula uses 24 since 24 is one less than the sample size of
25 (i.e., 24 is n-1). Note that D10 is the mean, while D16 is the standard error of
the mean. The above formula gives the lower limit of the confidence interval,
26.92.
F23:
=D10+TINV(1-.95,24)*D16
The above formula gives the upper limit of the confidence interval, 29.42.
Now, use number format (two decimal places) in your Excel spreadsheet for the
mean, standard deviation, standard error of the mean, and for both the lower limit
and the upper limit of your confidence interval. If you printed this spreadsheet
now, the lower limit of the confidence interval (26.92) and the upper limit of the
confidence interval (29.42) would ‘‘dribble over’’ onto a second printed page
because the information on the spreadsheet is too large to fit onto one page in its
present format.
So, you need to use Excel’s ‘‘Scale to Fit’’ commands that we discussed in
Chap. 2 (see Sect. 2.4 ) to reduce the size of the spreadsheet to 95 % of its current
size using the Page Layout/Scale to Fit function. Do that now, and notice that the
dotted line to the right of 26.92 and 29.42 indicates that these numbers would now
fit onto one page when the spreadsheet is printed out (see Fig. 3.4 ).
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