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# Quick Normal Distribution Question [+rep] Watch

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1. Hi,

I've got normal distribution, mean=1, variance=16 and trying to find P(X>-1.04). I've looked up what it should be by using online normal distribution calculators but keep getting the wrong answers. Can anyone help? +rep for help

Thank you!
2. Have you double checked you're using the right table?
Sounds daft, but a lot of the time when I got it wrong it's because the table was for values above instead of below etc.
Also - are you just using the variance value? Standard deviation is the square root of variance.
3. (Original post by sweetfloss)
Have you double checked you're using the right table?
Sounds daft, but a lot of the time when I got it wrong it's because the table was for values above instead of below etc.
Also - are you just using the variance value? Standard deviation is the square root of variance.
Thanks, I've been manipulating it to suit the particular table I'm using, and I am using the sd rather than the variance. Since you're 4th year maths, do I need to standardise before applying rules of symmetry or can I manipulate first and then standardise? My impression is it doesn't make a difference but I was only taught it 24 hours ago..
4. (Original post by GingerApple)
Thanks, I've been manipulating it to suit the particular table I'm using, and I am using the sd rather than the variance. Since you're 4th year maths, do I need to standardise before applying rules of symmetry or can I manipulate first and then standardise? My impression is it doesn't make a difference but I was only taught it 24 hours ago..
Shouldn't matter.
5. (Original post by sweetfloss)
Shouldn't matter.
If you say P(x>-1.04)=1-P(x<-1.04)=P(x<1.04)=P(z<0.01) or P(x>-1.04)=P(z>-0.51)=1-P(z<-0.51)=P(z<0.51) it does make a difference, doesn't it?

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Updated: December 4, 2010
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