relative frequency

A nurse measured the blood pressure of each person who visited her clinic. Following is a relative frequency histogram for the systolic blood pressure readings for those people aged between 25 and 40 years. The blood pressure readings (in mm Hg) were given to the nearest whole number. What class width was used to construct the relative frequency distribution? Systolic Blood Pressure for People Aged 25 - 40 Years W Click the icon to view the histogram for systolic blood pressure. A. 10 mm Hg O B. 9 mm Hg X C. 100 mm Hg Histogram for Systolic Blood Pressure O D. 11 mm Hg Relative Frequency 0.35 0.30 0.25 0.20 - 0.15