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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