The frequency histogram and grouped frequency table for the 52 time estimates contain similar information to the stem and leaf plot, but they don't indicate each person's actual estimate. The height of each bar in the histogram indicates the frequency of the corresponding interval of estimates on the horizontal axis. Note 4
As with the stem and leaf plot, the frequency histogram can be an awkward graph for large data sets, since the vertical axis corresponds to the frequency of each interval of values. For large data sets, some intervals may have many values and a high frequency. Consequently, the vertical axis would have to be scaled according to the largest frequency.
An alternative is to use relative frequencies to describe how many values are in each interval relative to the total number of values. For most purposes, relative frequencies are more useful than absolute frequencies; for example, the statement "17 of the 52 estimates are in the interval 50 to < 60" is more useful than the statement "17 estimates are in the interval 50 to < 60."
The relative frequency for the interval 50 to < 60 is 17/52, which you can also write in decimal form as .327 (rounded to three digits). Multiplying by 100 gives you the percentage, 32.7%. This means that 32.7% of the estimates are in the interval 50 to < 60.
Here is what you get for the rest of the data:
Notice that the relative frequencies expressed as fractions and decimals add up to 1 and that the percentages add up to 100%.