127 115 132 117 138 138 152 121 142 120 104 116 139 165 150 132 142 94 124 145
157 137 118 163 138 159 140 87 162 132 156 148 159 136 164 103 125 136 136 146
102 111 142 116 145 156 167 95 148 143 120 130 95 171 115 87 139 119 148 132
169 121 138 128 129 143 143 128 108 77 120 128 157 109 173 125 159 100 97 144
119 129 131 124 161 144 154 119 125 97 123 129 113 119 109 112 156 168 135 136
135 145 156 125 140 130 86 101 139 184 144 118 150 149 142 118 134 124 154 142
186 130 127 168 122 139 156 146 107 168 117 100 134 113 104 115 149 148 133 128
121 148 133 144 127 127 168 102 117 123 156 129 89 138 136 100 153 110 112 150
104 148 124 114 121 126 153 128 114 137 131 104 135 124 146 115 152 127 113 143
139 147 134 142 133 124 149 156 142 109 147 96 142 163 120 118 180 125 157 118
Table 11.2 Systolic Blood Pressure (mmHg)
measurements taken from 200 Random Individuals
Examine the data in table 11.2 and order the data in a tally sheet to form a
frequency table. Show that the smallest value is 74 and the largest value is 186.
Divide the data into categories or class intervals of equal length by defining an upper
limit and lower limit and midpoint for each class interval. This is called grouping
the data. Examples of class intervals are given in the table 11.3 where 74 is the
first midpoint with 16 midpoints to 186. If 74 + 16 x= 186, then x= 7 steps between
midpoints or the class interval is of size 7. Go through the data and find the number
of systolic blood pressures in each class interval. This is called determining the class
frequency associated with the grouped data. Then calculate the relative frequency
column, the cumulative frequency column and cumulative relative frequency column
as illustrated in the table 11.3. The cumulative frequency associated with a value x
is just the sum of the frequencies less than or equal to x. The cumulative relative
frequency is obtained by dividing the cumulative frequency by the sample size. Note
that the cumulative frequency ends in the sample size and the cumulative relative
frequency ends with 1.
