/* ---------------------------------------------------------------------- * This program reads a data sample from a text file in the format *                         one data point per line  * and calculates an interval estimate for the mean of that (unknown) much  * larger set of data from which this sample was drawn.  The data can be  * either discrete or continuous.  A compiled version of this program  * supports redirection and can used just like program uvs.c.  *  * Name              : estimate.c  (Interval Estimation)  * Author            : Steve Park & Dave Geyer  * Language          : ANSI C  * Latest Revision   : 11-16-98  * ---------------------------------------------------------------------- */#include <math.h>#include <stdio.h>#include "rvms.h"#define LOC 0.95                       /* level of confidence,        */                                        /* use 0.95 for 95% confidence */  int main(void){  long   n    = 0;                     /* counts data points */  double sum  = 0.0;  double mean = 0.0;  double data;  double stdev;  double u, t, w;  double diff;  while (!feof(stdin)) {                 /* use Welford's one-pass method */    scanf("%lf\n", &data);               /* to calculate the sample mean  */    n++;                                 /* and standard deviation        */    diff  = data - mean;    sum  += diff * diff * (n - 1.0) / n;    mean += diff / n;  }  stdev  = sqrt(sum / n);  if (n > 1) {    u = 1.0 - 0.5 * (1.0 - LOC);              /* interval parameter  */    t = idfStudent(n - 1, u);                 /* critical value of t */    w = t * stdev / sqrt(n - 1);              /* interval half width */    printf("\nbased upon %ld data points", n);    printf(" and with %d%% confidence\n", (int) (100.0 * LOC + 0.5));    printf("the expected value is in the interval");    printf("%10.2f +/- %6.2f\n", mean, w);  }  else    printf("ERROR - insufficient data\n");  return (0);}