Long answer·Hard exam skill (4/5)·No calculatorNeeds mentor review
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A grouped table has class intervals --- with frequencies
Total: 5 marks
(a) Write the class marks. (1 mark)
(b) Find the mean using class marks. (1 mark)
(c) Find the approximate variance and standard deviation using class marks. (3 marks)
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