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OCR S1 May 2006 Q7 - mean and standard deviation

Please may someone help to answer Q7a:

https://pmt.physicsandmathstutor.com/download/Maths/A-level/S1/Papers-OCR/June%202006%20QP%20-%20S1%20OCR.pdf

I don't know how to find the mean and standard deviation for this data.
(edited 10 months ago)
Reply 1
If it asks you to estimate it in this type of question, the best thing to do is to try to find midpoints for each of the groups (this is hinted by the "Assuming that ‘At least 60 minutes’ means ‘At least 60 minutes but less than 240 minutes’".

Once you find the midpoints, just treat the mean as it is normally :smile:
Reply 2
Original post by JJPSWFC
If it asks you to estimate it in this type of question, the best thing to do is to try to find midpoints for each of the groups (this is hinted by the "Assuming that ‘At least 60 minutes’ means ‘At least 60 minutes but less than 240 minutes’".

Once you find the midpoints, just treat the mean as it is normally :smile:

Thank you very much, now I understand it

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