Chapter 3

Q. 3.29

Systolic Blood Pressure

The frequency distribution for the systolic blood pressure readings (in millimeters of mercury, mm Hg) of 200 randomly selected college students is shown here. Construct a percentile graph.

A
Class
boundaries

B

Frequency

C
Cumulative
frequency
D
Cumulative
percent
89.5–104.5 24
104.5–119.5 62
119.5–134.5 72
134.5–149.5 26
149.5–164.5 12
164.5–179.5     4
200

Step-by-Step

Verified Solution

Step 1 Find the cumulative frequencies and place them in column C.
Step 2 Find the cumulative percentages and place them in column D. To do this step, use the formula

Cumulative % =\frac{\text{cumulative frequency}}{n} · 100

For the first class,

Cumulative % =\frac{24}{200} · 100 = 12%

The completed table is shown here.

Step 3 Graph the data, using class boundaries for the x axis and the percentages for the y axis, as shown in Figure 3–6.

A
Class
boundaries
B

Frequency

C
Cumulative
frequency
D
Cumulative
percent
89.5–104.5 24 24 12
104.5–119.5 62 86 43
119.5–134.5 72 158 79
134.5–149.5 26 184 92
149.5–164.5 12 196 98
164.5–179.5   4 200 100
200
3.6