Write an equation of the line passing through the points (4,15) and (-1, 15)

Find slope: (15-15)/(-1-4) = 0/-5 = 0
Y = 0x + b
15 = 0(4) + b, b = 15
Equation: y = 0x + 15
Or... y = 15

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.