"Biff" wrote:
Don't know what is meant by a frequency histogram and a
relative frequency histogram.

In the first case, the y-axis is the frequency represented by each
bin, as you might be used to. In the second case, the y-axis is
the percentage of the total in each bin-- the bin frequency divided
by the sum of the frequencies (total number of data).

Two distributions can have the same relative frequency
histogram, but different frequency histograms. For example,
consider a uniform distribution of 1000 data and 10000 data
over 10 bins. In the frequency histogram, the y-axis is 100
and 1000 respectively. In the relative frequency histogram,
the y-axis is 0.1 in both cases.