How to solve ncdf(X, 0.76, 83, 1E99) = 0.15 (RESOLVED)

[Tim Wessman]

Simpler actually (although you could do it the same way if you really wanted). NOTE: I can add some pictures later if you want.

Open solve app. Remember that most applications have a symbolic, plot and numerical representation. Pressing the Symb, Plot or Numeric buttons will switch between them.

In Symb view, type NORMALD_CDF(X,.76,83,1E99)=.15 (the "maximum" real value is actually 1E499, so you could replace "1E99" by "MAXREAL" if desired)

The press Num to go to the solver. Press SOLVE on the screen button to solve numerically. Plot will open a plot and you can view the crossing point if desired with a bit of scrolling/adjustment/scaling.

Now if you want to do the exact same way with the function application, you can do so. Just define F1(X) as NORMALD_CDF(X,.76,83,MAXREAL) and F2(X)=.15. Plot to see the plot, Menu button on the screen -> Fnc -> Intersection to jump to your intersection (no left/right needed). Did you want to look at a table instead and "manually" figure out the X value? Well, just press num. You can see the value of F1(X). Type a number to jump to that location. As you approach your value, you will see the values approaching 1 the closer you get.


You also have the option of defining your solve equation, E1 as NORMALD_CDF(X,S,L,U)=P. Then you will get 4 variables to fill in with desired values and solve for the last one. Very flexible. :-)