The scores on a psychology exam were normally distributed with a mean of 56 and a standard deviation of 9. A failing grade on the exam was anything 2 or more standard deviations below the mean. What was the cutoff for a failing score?

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.