ABSTRACT
At the beginning of this chapter the frequency distribution of data from a picturenaming task was reported (Table 2.1). When we know that each score xi occurs with frequency fi, there is also an alternative formula for calculating the mean of a frequency distribution. This alternative formula is based on the fact that the sum of the frequencies at which each score occurs is equal to the total number of observations; thus, the mean is given by:
l = =
f x
f
where the numerator is the sum of the products of each observed value (i.e., xi) multiplied by its frequency (i.e., fi), for each of the m values of x, and the denominator is the sum of the frequencies of each observed value, i.e., n. This formula will turn out to be useful when, in Chapter 4, we calculate the mean of probability distributions.
