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# S1 normal distribution question Watch

1. Hi, im struggling with this question

when you look up 0.9300 in the normal dist. table, you have to choose between

1.47- 0.9292
1.48-0.9306

do you pick P(z<1.48) cos its closer to 0.9300? if so, how did they get 1.476..i.e how do you precisely pick which one is more appropriate?
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2. bump?
3. Same thing happened to us in class. Our teacher told us that should never happen in a real exam, that all of the answers would be accurate if we'd got them right, but for the purposes of those questions to either use the closest or make an estimate. Do you have the answer sheet to work out what they wanted?

We were told it was because different people print different values, so if you use say an Edexcel worksheet with an independent ND table, you're likely not to find the results you need.
4. This is probably an old paper. They used to do it by linear interpolation. It's in FP1 but it's fairly simple (I think). It's basically the "fraction of the way along" is the correct value. 0.93 is 0.008 above the lower value (which is 0.9292, corresponding to 1.47), out of a total 'gap' of 0.014. 0.008/0.014 = 0.6, to 1 decimal place. So 60% of the way between 1.47 and 1.48 is the correct value, i.e. 1.476.

But don't worry, you don't have to do it!
5. (Original post by starkrush)
This is probably an old paper. They used to do it by linear interpolation. It's in FP1 but it's fairly simple (I think). It's basically the "fraction of the way along" is the correct value. 0.93 is 0.008 above the lower value (which is 0.9292, corresponding to 1.47), out of a total 'gap' of 0.014. 0.008/0.014 = 0.6, to 1 decimal place. So 60% of the way between 1.47 and 1.48 is the correct value, i.e. 1.476.

But don't worry, you don't have to do it!
I know how to do linear interpolation :P I sat FP1 in Jan!

Thanks for the help guys
6. I'd pick the closest one...

Updated: April 15, 2012
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