The first quartile - Math Central

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Hi,

Please help me solve this question.

Thank you so much.

The cumulative frequency table below shows the length of time that 30 students spent text messaging on a weekend.

Minutes Used	Cumulative Frequency
31-40	2
31-50	5
31-60	10
31-70	19
31-80	30

Which 10-minute interval contains the first quartile?

(1) 31–40

(2) 41–50

(3) 51–60

(4) 61–70

Hi,

This is worded strangely. I think the question should be "Which 10-minute interval contains the boundary between the first quartile and the second quartile? "

There are 30 observations in total so the boundary between the first and second quartile is at 30/4 = 7.5. In which 10 minute interval would you find 7.5?

Penny

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