FRAME 23.
In the example above, we indicated the total of several measurements by using the term "sum
of." We use this term so frequently that we have accepted a symbol to replace the words. The
symbol is the Greek letter Σ (pronounced Sigma). Thus, we could have expressed the problem
as follows:
Σ (test scores)___
mean score =
number of test scores
Since we do not limit ourselves to finding Just average test scores, we need to develop a
more general statement for the relationship among the sum of the items we are interested in, the
number of those items, and the mean value of those items. Such a general statement is called a
formula. The formula is like a recipe, or set of general directions. It is composed of general
symbols that we attach specific values to for specific problems. For example, the formula for the
sample mean is:
X = ΣX
n
Where,
X is the symbol for the sample mean,
X is the symbol for each observation of interest, and
n is the symbol for the number of observations.
In the example above, we are interested in 5 ages, thus X in this example represents each of the
given ages. ΣX represents the sum of the five ages. For each problem we do, or situation we
encounter, what X represents will be specified.
FRAME 24.
Answer the following questions below using the following five dollar amounts, , , ,
, taken from a group of 100 dollar amounts.
a. X represents ___, ___, ___, ___, ___
b. ΣX = ___
c. n = ___
d. ΣX = ___
n
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FI0921
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