The following table shows a frequency distribution for grouped data. Notice that the frequency of scores, f(x), does not add up to 15. If a total of 15 scores were actually counted, which of the following gives an explanation for why the frequencies do not add up to 15?

Intervals Frequency 0–5 4 5–10 6 10–15 3 15–20 5

a. There are too many intervals for the data counted, which might lead to a larger total than the number of scores counted.

b. There are too few intervals for the data counted, which might lead to a smaller total than the number of scores counted.

c. The intervals overlap at the upper and lower boundaries, which might lead to some scores being counted in more than one interval.