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

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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