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[amjad]

How i can use normal distribution function table in casio 991 ES calculator, e.g P(Z< 1.98)= ?

[weatherhead]

The distribution functions on the 991 are a little bit limited, not well labelled, and not that easy to find. Also they are only to 5 decimal places, which seems a bit silly to me. In the UK the tables you get with a statistics exam show it to 5 d.p for input values sensitivity 0.01, so the calculator doesn't do that much better for accuracty. Anyway, you can get at the Z function with a few button presses like this:

1.go into "stat" mode (mode button, then button number 3)
2. choose "1-var" (button number 1)
3.Drop out of the table editor by pressing AC
4.Go into the stats menu (shift then button 1, labelled "stat" above it)
5.press number 7 (for "Distr")
6.Choose which CDF you want. P( (number 1) means P(z<=x). Play around to find the others, I don'[t remember exactly which ones they are... except that >t is obviously converting to student's T distribution
7.Enter the probability
8.If you want to use this number in "normal" mode, save it to a variable (shift, RCL, A)
9.Revell in statistical goodness