Stapplet App to Calculate a Probability
For Operation select "Calculate an area under the Normal Curve"
Enter the mean and the standard deviation.
If you are using Z values, the mean is 0 and the standard deviation is 1.
If using X values, just enter the given mean and standard deviation.
Note that if you are calculating probabilities for a mean, you must divide the given standard deviation for the population by the square root of the sample size and use the new standard deviation for a mean.
Choose which area to calculate. The following directions also work with Z scores.
For P( X< x1) select the area "to the left of a value" and enter x1 in the box.
For P (X > x1) select the area "to the right of a value" and enter x1 in the box.
If calculating P(x1 < x < x2) then select the area "between two values" and enter x1 in the Left boundary box and x2 in the right boundary box.
If calculating P(x < x1) with P(x >x2) then select the area "outside a region" and enter x1 in the Left boundary box and x2 in the right boundary box.
Then press "Calculate area". Your answer should be somewhere between 0 and 1 since these are the only possible values for probabilities.