Question

Here is a data set: 123 139 165 168 155 108 258 130 183 157 137 93 188 154 188 172 195 133 99 134 160 119 132 178 153 63 179 109 The goal is to construct a grouped frequency distribution table (GFDT) for this data set. The GFDT should have 10 classes with a "nice" class width. Each class should contain its lower class limit, and the lower class limits should all be multiples of the class width. This problem is to determine what the class width and the first lower class limit should be. What is the best class width for this data set? optimal class width = Correct What should be the first lower class limit? 1st lower class limit=

Answer 1

Let's say number of observations n, n=28

and the number of classes required k, k=10

We will find the class width with the formula = (maximum value-minimum value )/k =   (258-63)/10= 195/10= 19.5= 20(approx.)

So class width is 20, and the first lower class limit will be 60 as it is closer to our minimum observation

therefore the grouped frequency distribution table is

C.I frequency

60-80 1

80-100 2

100-120 3

120-140 7

140-160 5

160-180 5

180-200 4

200-220 0

220-240 0

240-260 1