+33654 I take it this means the normal cumulative distribution function. Here is a graph of the normal cdf for a mean of 0 and standard deviation of 1:
If you have a data set x1, x2, etc. for which you know the mean, xav, and standard deviation, s, and want to find the cumulative probability for a particular value of x, then calculate z = (x-xav)/s and look up the corresponding value of cumulative probability (called cnorm(z) on the graph above). You should be able to find better graphs if you search the internet. Alternatively, use a piece of software which will calculate it for you, given the values of xav and s (again you can almost certainly find something on the internet to do this).
Or, if you are old-fashioned, use tables of values that are printed in books!
+33654 I take it this means the normal cumulative distribution function. Here is a graph of the normal cdf for a mean of 0 and standard deviation of 1:
If you have a data set x1, x2, etc. for which you know the mean, xav, and standard deviation, s, and want to find the cumulative probability for a particular value of x, then calculate z = (x-xav)/s and look up the corresponding value of cumulative probability (called cnorm(z) on the graph above). You should be able to find better graphs if you search the internet. Alternatively, use a piece of software which will calculate it for you, given the values of xav and s (again you can almost certainly find something on the internet to do this).
Or, if you are old-fashioned, use tables of values that are printed in books!
