How do I calculate the probability of a value being between 60.5 and 70.5 when the standard deviation is 2.5 and the mean is 65.5?

Question

campbell_st · Answer

well 70.5 is    65.5 + 2x 2.5  

so 70.5 is 2 standard deviations above the mean

60.5   is  65.5 - 2x2.5 

so 60.5 is 2 standard deviations below the mean... 

attached is an image of the standard Normal curve... 0 is the mean so you want the total of the percentages between -2 and 2

hope it helps

anonymous · Answer

ok, so if I ever have a problem like that, I just need to find how many standard deviations  is the mean from the bounds and then add the percentages related to each standard deviation?

anonymous · Answer

the sum would be 95%. Wow! I was busting my brain over nothing!

campbell_st · Answer

that's correct.