The actual sales for the same month for the last 4 years have been 24 units, 30 units, 23 units, and 27 units. what is the average number of units you can expect to sell next month?

24 + 30 + 23 + 27 = 104
104/4 = 26
Average number of units you can expect to sell next month is: 26 units

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.