Re: please check my homework

Michael Jørgensen wrote: 
"David Marsh" <dmarsh@xxxxxxxx> wrote in message
news:sAw7f.306880$tl2.244927@xxxxxxxxxxx

This is a homework assignment for extra credit. The statistical
material has not been covered in class. Is my bidist() function
correct? It seems to work with the examples I have tried, but I
would appreciate your comments and suggestions. PLEASE don't
write any code. Error checking deliberately omitted for now and I
am aware of the potential for factorials to exceed LDBL_MAX.

David
---------------------------------------------------------------


<snip code>

Write also a test function that calculates: f(0) + f(1) + f(2) + ... +
f(n-1) + f(n). This sum should be exactly 1.0 for all valid values of n and
p.


/* test function -- when plotted, the intermediate values
   produce the curve of the binomial distribution */
void bidist_test(long double p, long double n, long double x)
{
    long double fn, fx, fnx, t1, t2, t3;
    long double sum, xx, ival;

    sum = 0.0;
    for(xx = 0.0; xx <= n; xx++)
    {
        fn = factorial(n);
        fx = factorial(xx);
        fnx = factorial(n-xx);
        t1 = fn / (fx * fnx);
        t2 = (long double)pow(p, xx);
        t3 = (long double)pow(1.0-p, n-xx);
        ival = t1 * t2 * t3;
        sum += ival;
        printf("%Lf\n", ival);
    }
    printf("\n%Lf\n", sum);
    return;
}

sample output:
p=.5, n=12, x=5

0.000244
0.002929
0.016113
0.053710
0.120850
0.193359
0.225586
0.193359
0.120850
0.053710
0.016113
0.002929
0.000244

1.000000

David
.

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