36
26 The binomial distribution
Assume that the probability that a tossed coin will land showing “heads” is , and that the
probability for “tails” is ( ). Then over tosses, the probability that the coin will land
times with “heads”-up, is:
Program
?→ A:?→ B:?→ X:BCX × A ^ X(1- A)^(B - X)→ Y:Y < 34 STEP >
C:
INPUT A: throws B: probability of “heads” X: number of “heads”
Execution Example:
For a coin with probability of landing “heads”,
find the probability of getting 3 “heads” out of 7 throws.
1 p– x
x() C
m
p
x
x
1p–()
mx–
=
nCr
1
3
---
Prog
1
S A
D R
P1
P2 P3 P4
G
1 3
EXE
S A
D R
P1
P2 P3 P4
G
7
EXE
S A
D R
P1
P2 P3 P4
G
3
EXE
S A
D R
P1
P2 P3 P4
G
関数電卓事例集 .book 36 ページ 2002年9月2日 月曜日 午後6時51分