Given the data below representing the body mass index (bmi) values for 20 females.
17.7 33.5 26.9 22.7 22.2 29.9 23.6 18.3 27.7 23.4 19.2 25.9 22.9 37.7 31.6 28.1 44.9 31.6 25.2 23.9
From the data above, we construct a frequency distribution beginning with a lower class limit of 15.0 and use a class width of 6.0 as follows:
Class iinterval: 15.0 - 21.0 21.0 - 27.0 27.0 - 33.0 33.0 - 39.0 39.0 - 45.0
Frequency: 3 9 5 2 1
From the frequency table, it can be seen that the frequencies started low, increased to a point and then decrease. It can also be seen that the highest frequency of the data is not at the center of the distribution, so the distribution is not symetric.
Therefore, the frequency distribution does not appear to be roughly a normal distribution, because, "although the frequency start low, increase to some maximum, then decrease, the distribution is not symmetric."