Mathematics
OpenStudy (anonymous):

Super-urgent! About statistics and probability. What is the difference between using the command normalpdf and the command normalcdf? Which I use to find out one thing vs another thing?

OpenStudy (kinggeorge):

the cdf is cumulative. So if you want to find the normal up to a certain z, use cdf.

OpenStudy (kinggeorge):

the pdf is a version where it's looking at a specific value.

OpenStudy (kinggeorge):

Looking at my own calculator (casio not TI), using the cdf I get a value for the area under the normal curve with a given lower bound and a given upper bound along with a standard deviation and a mean.

OpenStudy (kinggeorge):

I'm also a little unclear about the meaning of the pdf however. I know it's for a specific value, and the function takes a mean, standard deviation, and x value.

OpenStudy (anonymous):

cdf gives the propability that a value less than something or greater than something occurs? pdf is the prob of a single value occurring when a value is random selected from a set? Also what does Z = (X-mu(weird greek letter) / sigma) stand for? What do the terms Z and X stand for?

OpenStudy (kinggeorge):

The best explanation I can find for the pdf, is that it gives the value of the derivative of the cdf at a certain value. So the graph of the cdf looks something like|dw:1338180206660:dw|and the pdf looks at the derivative of that graph. Meanwhile, the cdf calculates the area under the curve|dw:1338180272473:dw|which is a graph of the pdf.