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S2 Normal distribution to 4dp

On the MEI 2009 S2 paper (q 3i A), you are told to find the probability that Z is less than a number. In the mark scheme, it says you have to find the number, and then the probability, to 4 decimal places, but I thought the normal tables only went to 3dp (for the number Z is less than). How do you find P(Z<k), where k is to 4 decimal places?

Thanks

Edit: This is from the mark scheme

= P( Z < 0.2146)
= Φ(0.2146) = 0.5849
(edited 12 years ago)
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MrGum
You need to check out MEI's take on such things. See the note on accuracy in statistics in
http://www.mei.org.uk/files/pdf/OCR_MEI_Maths_rep_10_gce_jun.pdf

It seems that MEI do require use of interpolation from tables. So if you want Φ(0.8733)\Phi(0.8733) and your tables only give Φ(0.873)\Phi(0.873) and Φ(0.874)\Phi(0.874), you choose a value three tenths of the way up the interval between these answers.
Original post by Mr Gum
You need to check out MEI's take on such things. See the note on accuracy in statistics in
http://www.mei.org.uk/files/pdf/OCR_MEI_Maths_rep_10_gce_jun.pdf

It seems that MEI do require use of interpolation from tables. So if you want Φ(0.8733)\Phi(0.8733) and your tables only give Φ(0.873)\Phi(0.873) and Φ(0.874)\Phi(0.874), you choose a value three tenths of the way up the interval between these answers.


Thank you ever so much for this! :smile:

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