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# S2 : normal distribution : if z<3.27 should table probability be z<3.25? Watch

1. Or z< 3.30? A book example writes that the closest table probability is z<3.25 so we can approximate it to that. Given the great number of errors in the book, i decided to ask here to confirm if the book is correct.

My 2nd question: if z< 3.27 should make us choose the table probability for z<3.25, When would we choose z<3.3 as the table value instead of 3.25?
2. (Original post by chhhhelsie)
Or z< 3.30? A book example writes that the closest table probability is z<3.25 so we can approximate it to that. Given the great number of errors in the book, i decided to ask here to confirm if the book is correct.My 2nd question: if z< 3.27 should make us choose the table probability for z<3.25, When would we choose z<3.3 as the table value instead of 3.25?

z < 3.3 = 0.99952

z < 2.27 = 0.98840

Just use this: http://filestore.aqa.org.uk/subjects/FORMULAE.PDF (Page 24) for the full table if you don't have any better.

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Updated: June 25, 2016
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