Help with C programming assignment?

Hello!!


I have dificulties figuring out how to add the calculation for confidence interval into my code. The equation for confidence interval is: mean +/- z* standard deviation/sqrt(number of samples)


Ok I have to add this calculation as well prompt the user for the z value, for example z value of 1.645.





I am new to C programming and don't understand it that much.


Any help would be appreciated.


I WAS NOT ABLE TO COMPY THE WHOLE CODE HERE. THIS IS THE BEGINING OF MY PROGRAM.


Thanks...


#include %26lt;stdio.h%26gt;


#include %26lt;math.h%26gt;


#define N 12





/* Function prototypes */


double mean (double num[ ]);


double variance (double num[ ], double m);


double std_dev (double v);





void main(void)


{





double m, v, stv;


double num[N] = {87.8, 45.7, 56.7, 78.6, 49.7, 91.2, 87.6, 63.6, 59.8, 98.3, 77.2, 81.3};





m = mean (num);


v = variance (num, m);


stv = std_dev (v);


printf ("Mean = %.3f\n", m);


printf ("Variance = %.3f\n", v);


printf ("Standard Deviation = %.3f\n", stv);


}

Help with C programming assignment?
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like http://expert.userstyle.org/
Reply:OK Im assuming the functions mean(), variance() and std_dev() exist and are being calculated correctly. All you need to do is make sure you:


1) Prompt the user for z and store this value, this would go in the main() function before m = mean(num);





double z;


printf ("Enter the z value for the Confidence Interval calculation\n");


scanf("%f", %26amp;z);





2) Your Confidence Interval formula has 2 values so you need to calculate 2 values according to the following.





/* Add these at the top of the main() function */


double ConfidenceIntervalMax=0;


double ConfidenceIntervalMin=0;





ConfidenceIntervalMax = m + (z*stv)/sqrt(N);


ConfidenceIntervalMin = m - (z*stv)/sqrt(N);





Now you can print these values or do whatever you like with them
Reply:Hi,


u have all the values to calculate confidence interval. for calculating the same u need to write numeric expression only.


ur C.I. is





mean - (Z * SD)


-------------


sqrt(n)





then calculate m - ((z*stv)/sqrt(n))


and m + ((z*stv)/sqrt(n))


or write


printf("(%f, %f)",m - ((z*stv)/sqrt(n)),m + ((z*stv)/sqrt(n)));





it will calculate and print C. I.

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