For which of the following displays of data is it not possible to find the mean?

frequency table

dot plot

stem-and-leaf plot

histogram

Answer: Histogram

You can eliminate the stem and leaf plot, since it tells you the amount of values.

You can eliminate the dot plot, since it also shows you the number of values.

You can eliminate the frequency table, since it calculates the frequency of a number.

Thus, the answer is the histogram.