4.1 Coded Formula
The computation of the mean can be facilitated by using the coded formula which is shown below:

where:
X_am = assumed mean
f = frequency
d = coded deviation
n = total frequency
i = class size

To find the mean using the coded formula, the following procedure may be employed:
1. Choose any class interval as the assumed mean. The class mark of this class interval will be our
2. Construct the column for the deviation (d). This is done by putting 0 as the deviation for our assumed mean (deviation from itself). For the class intervals larger than the class interval which contains the assumed mean, the deviations are 1, 2, 3, and so on. For the class intervals smaller than the class interval which contains the assumed mean, the deviations are -1, -2, -3, and so on in that order.
3. Multiply each frequency by the corresponding deviation to get the entries in the fd column.
4. Get the sum of the value obtained in step 3 to obtain
5. Use the formula to compute the mean.

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