# Computing Probabilities of a Trinomial Distribution

Version 1.0

© Bin Wang 2008.
The following program provides a tool to compute the trinomial probabilities with formula

f(x_{1}, x_{2}, x_{3}; n, p_{1}, p_{2}, p_{3}) = P(X_{1}=x_{1}, X_{2}=x_{2}, X_{3}=x_{3}) = n!/(x_{1}!.x_{2}!.x_{3}!).p_{1}^{x1}.p_{2}^{x2}.p_{3}^{x3}

where x_{1}+x_{2}+x_{3}=n and p_{1}+p_{2}+p_{3}=1 and

n: the total number of trials;
( n=5,10,15,20,30,60).

x_{1}: number of times that outcome 1 was observed;

x_{2}: number of times that outcome 2 was observed;
( x_{2}=0,1,2,3).

x_{3}: number of times that outcome 2 was observed;
( x_{3}=0).

p_{1}: probability that outcome 1 will be observed in one trial;

p_{2}: probability that outcome 2 will be observed in one trial;
( p_{2}=0.05, 0.10, 0.15, 0.20, 0.25, 0.30).

p_{3}: probability that outcome 3 will be observed in one trial;
( p_{3}=0.05, 0.10, 0.15, 0.20).

Invalid parameter!: n =

Invalid parameter: x_{2} =

Invalid parameter: x_{3} =

Invalid parameter: p_{2} =

Invalid parameter: p_{3} =