- A11
- B17
- C13
- D19
Step-by-Step Solution
Add the frequencies of every class below 160: 6 + 11 = 17 students. The remaining 8 + 5 = 13 students are 160 cm or taller.
Answer: B) 17
A histogram of the heights of students uses these classes and frequencies. 140–150: 6, 150–160: 11, 160–170: 8, 170–180: 5. How many students are shorter than 160 cm?
Class 9StatisticsStatistics and Probability
Key idea: Histogram vs bar graph
Both look like bars, but they differ:
**Bar graph**: For DISCRETE / categorical data (favourite colour, sport, etc.). Bars have GAPS between them. Width has no meaning.
**Histogram**: For CONTINUOUS / grouped data with class intervals. Bars TOUCH (no gaps), reflecting that the class boundaries are continuous. Bar WIDTH represents class size; HEIGHT represents frequency.
**Frequency polygon**: connect the midpoints (class marks) of the tops of histogram bars to form a line graph. Useful for comparing two distributions on the same axes.
**Key rule**: histogram bars must have no gaps; bar graph bars MUST have gaps.
**Bar graph**: For DISCRETE / categorical data (favourite colour, sport, etc.). Bars have GAPS between them. Width has no meaning.
**Histogram**: For CONTINUOUS / grouped data with class intervals. Bars TOUCH (no gaps), reflecting that the class boundaries are continuous. Bar WIDTH represents class size; HEIGHT represents frequency.
**Frequency polygon**: connect the midpoints (class marks) of the tops of histogram bars to form a line graph. Useful for comparing two distributions on the same axes.
**Key rule**: histogram bars must have no gaps; bar graph bars MUST have gaps.
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