^{How to decide on the number of classes for a frequency distiribution.}
A useful recipe to determine the number of classes (k)is the “2 to the k rule.” such that 2^{k} > n.
i.e. There were 180 vehicles sold, so n = 180. If we try k =7, then 2^{7} = 128, somewhat less than 180. Hence, 7 is not enough classes. If we let k = 8, then 28 = 256, which is greater than 180. So the recommended number of classes is 8.