HP 20B - Manual (Page 25)

Mathematical Calculations
25
Table 2-5 Math Menu Example
Keys Display Description
.5I
:s Enters 0.5 and opens the Math menu starting with
Trigonometry.
I<
Selects the Trigonometry sub-menu and scrolls to Sin-1.
Note the value for Sin-1 is calculated immediately and
displayed.
I
or
= Validates the result.
In the Math menu, PI does not perform calculations; it enters PI for calculations. You may start an operation, use the Math
menu to execute a function, and continue calculating with your original operation without losing your work.
The Probability Sub-menu
Lower Tail Normal Distribution (LTND) calculates the probability for a normally distributed, random variable to be less than the
input.
Inverse Lower Tail Normal Distribution (LTND -1 ) is the inverse function for LTND; it calculates the value (V) for which the
probability of a normally distributed, random variable to be less than V is the given input. Student, Inverse Student, Chi 2 ,
Inverse Chi 2 , F-Distribution and Inverse F-Distribution perform similar operations for Student, Chi 2 , and F-Distributions.
Student, Chi 2 , and F-Distribution and their inverse operations are special cases, as they require more than one number as
input. Student and Chi 2 require (N), the number of degrees of freedom, and F-Distribution requires (N1) and (N2), two degrees
of freedom.
To perform Student and Chi 2 operations or their inverse:
1. Enter the number of degree(s) of freedom by typing the number and pressing
I
or
=
.
2. Type the number for which you want to calculate the probability, or, for the inverse, the probability for which
you want the number.
3. Navigate to the appropriate function in the Probability sub-menu of the Math menu.
To perform F-Distribution operations or their inverse:
1. Enter the two degrees of freedom by typing each number followed by
I
or
=
.