Statistics and Probability · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
1. What does 'cumulative frequency' of a class mean?
- AThe frequency of that class only
- BThe sum of frequencies of that class and all classes before it
- CThe total of all frequencies in the table
- DThe midpoint of the class
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Answer: B) The sum of frequencies of that class and all classes before it
Cumulative frequency (less than type) is obtained by adding up the frequency of a class and all classes preceding it.
2. The cumulative frequency of the last class in a 'more than' distribution equals the frequency of:
- Athe first class
- Bthe last class
- Cthe whole data set
- Dzero
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Answer: B) the last class
In a more-than table, the last entry equals the frequency of the last class alone (no class beyond it).
3. To draw an ogive for class intervals 1-10, 11-20, 21-30 (inclusive form), we must first convert them to:
- Aclass marks only
- Bcontinuous (exclusive) class boundaries
- Cpercentages
- Dratios
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Answer: B) continuous (exclusive) class boundaries
Inclusive classes are made continuous (0.5-10.5, 10.5-20.5, ...) before plotting an ogive.
5. A less-than ogive for 100 students' marks is given by the points (20,10),(40,30),(60,55),(80,85),(100,100).
Using graphical estimation, between which two consecutive points does the median (2N = 50) lie, and is it in the class 40-60?
- ABetween (20,10) and (40,30); class 20-40
- BBetween (40,30) and (60,55); class 40-60
- CBetween (60,55) and (80,85); class 60-80
- DBetween (80,85) and (100,100); class 80-100
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Answer: B) Between (40,30) and (60,55); class 40-60
2N = 50 lies between cf = 30 (at 40) and cf = 55 (at 60), so the median falls in the class 40-60.