Question

a pediatrician tested the cholesterol levels of several young patients. the following relative-frequency histogram shows the readings for some patients who had high cholesterol levels.

histogram: x-axis cholesterol level (195, 205, 215, 225); y-axis relative frequency (0 to 0.5)

use the graph to answer the following questions. note that cholesterol levels are always expressed as whole numbers.

a. what percentage of patients have cholesterol levels between 195 and 199, inclusive?
□ %

b. what percentage of patients have levels of 215 or higher?
□ %

c. if the number of patients is 20, how many have levels between 205 and 209, inclusive?
□ patients

Explanation:

Part a

Step1: Identify the bar for 195 - 199

From the histogram, the relative frequency for 195 - 199 is 0.15 (assuming each grid line is 0.05, and the bar reaches 0.15).

Step2: Convert to percentage

To find the percentage, multiply the relative frequency by 100: $0.15\times100 = 15$

Step1: Identify bars for 215 or higher

The bars for 215 - 219 and 225 -... (the last bar). The relative frequency for 215 - 219 is 0.15 and for 225 -... is 0.05 (assuming grid lines).

Step2: Sum relative frequencies

Sum: $0.15 + 0.05 = 0.2$

Step3: Convert to percentage

Multiply by 100: $0.2\times100 = 20$

Step1: Identify relative frequency for 205 - 209

From the histogram, the relative frequency for 205 - 209 is 0.15 (assuming grid lines).

Step2: Calculate number of patients

Number of patients = total patients × relative frequency = $20\times0.15 = 3$

Answer:

15%

Part b