HP 39gs Master Manual page 233

Equations and
E1 E2
These two equations can be used for calculations involving individual and cumulative Binomial probabilities.
eg. Find the probability of at most 3 heads when
tossing a coin 10 times.
Ensure that formula
the values shown right. The value in
irrelevant as it is merely the summation variable.
Highlight and press
V
Answer: 0.1719
Note:
If N is larger than 200 then you should use a Normal approximation. The
the formula will cause internal overflow and inaccurate answers above this level. The time needed to
perform the summation will probably also be excessive. Solve works by repeated iterations
converging on the correct value and this will be quite slow if the summation has many terms. If it is
important not to use a Normal approximation then replace the
. The
COMB(N,R)
greatly with the iteration time needed.
Equations and
E3 E4
These two equations can be used for calculations involving individual and cumulative Poisson probabilities,
where is the mean. The technique is otherwise identical to the Binomial problem.
M
Equation
E5
The formula in is a generic formula for problems such as the one below:
E5
"A probability distribution has the equation f x ) = 0.625 x
that this is a valid probability distribution function and use it to find P x ≤ 1.2
Use it by substituting whatever function is in use for the one currently entered. As this formula involves the
integration function, each use of the solve process will require the calculator to perform multiple integrations.
Because of this the solving process will be relatively slow.
is ed and enter
E2
is
J
.
function has special facilities for handling large numbers. This will not help
COMB
N!/((N-R)!*R!)
( )
; 0 ≤ x ≤ 2 . Show
2 − x
3
(
233
section of
N!/((N-R)!*R!)
portion with
( )
"