Microsoft Office Tutorials and References

In Depth Information

Chapter 1

Sample Size, Mean, Standard Deviation,

and Standard Error of the Mean

This chapter deals with how you can use Excel to ﬁnd the average (i.e., “mean”) of a

set of scores, the standard deviation of these scores (STDEV), and the standard error

of the mean (s.e.) of these scores. All three of these statistics are used frequently and

form the basis for additional statistical tests.

1.1 Mean

The
mean
is the “arithmetic average” of a set of scores. When my daughter was in

the ﬁfth grade, she came home from school with a sad face and said that she didn’t

get “averages.” The book she was using described how to ﬁnd the mean of a set of

scores, and so I said to her:

“Jennifer, you add up all the scores and divide by the number of numbers that you have.”

She gave me “that look,” and said: “Dad, this is serious!” She thought I was teasing her. So I

said:

“See these numbers in your book; add them up. What is the answer?” (She did that.)

“Now, how many numbers do you have?” (She answered that question.)

“Then, take the number you got when you added up the numbers, and divide that number by

the number of numbers that you have.”

She did that, and found the correct answer. You will use that same reasoning

now, but it will be much easier for you because Excel will do all of the steps for you.

We will call this average of the scores the “mean” which we will symbolize as
:

X
, and we will pronounce it as: “Xbar.”

The formula for ﬁnding the mean with you calculator looks like this:

P
X

n
:

X

¼

(1.1)

T.J. Quirk et al.,
Excel 2007 for Biological and Life Sciences Statistics
,

DOI 10.1007/978-1-4614-6003-9_1,
#
Springer Science+Business Media New York 2013

1

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