The data set of the sample is
62 82 79 76 73 70 67 64 61 66 66 66 63 63 63 60 60 71 71
we have that
(84.5-59.5)/5=5
therefore
The classes are equal to
N 1) 59.5-64.5 ------> midpoint 62
N2) 64.5-69.5 -----> midpoint 67
N3) 69.5-74.5 -----> midpoint 72
N4) 74.5-79.5 -----> midpoint 77
N5) 79.5-84.5 -----> midpoint 82
Find out the frequency for each class
N 1) 59.5-64.5 ------> 8
N2) 64.5-69.5 ----->4
N3) 69.5-74.5 ----> 4
N4) 74.5-79.5 ------> 2
N5) 79.5-84.5 ----> 1
see the figure below to better understand the problem
