PROBLEM: Thestandarddeviationofalistofnumbersisameasureofhowmuchthenumbers devia

Question

PROBLEM:

Thestandarddeviationofalistofnumbersisameasureofhowmuchthenumbers

deviatefromtheaverage.Ifthestandarddeviationissmall,thenumbersare

clusteredcloseto theaverage.Ifthestandarddeviationislarge,thenumbersare

scatteredfarfromtheaverage.Thestandarddeviation,S,ofalistofNnumbersxi is

definedasfollows,

S =      

where x istheaverageoftheNnumbersx1,x2,....Defineafunctionthattakesan

arrayofnumbersasitsargumentandreturnsthestandarddeviationofthe

numbersinthearray.Yourfunctionshouldhave twoparameters:anarray

parameterandaformalparameteroftypeint thatgives thesizeofthearray.The

numbersinthearraywillbeoftypedouble,butwillnotbenegative. Tostart,use

aconstintsetto5todefinethesizeofthearrayandallowtheusertoinputthat

manynumberstofillit.

Yourmainprogramshouldaccepttheinputtofillthearray,makeacalltothe

functiontocalculatethestandarddeviation,andthenoutputtheresult.

Forextracredit,allowtheusertoinputasmanyvaluesastheywouldlike (upto

20). Thencallthefunctionwiththepartiallyfilledarray.

hint:

1). Rememberthefunctionsqrt()

2). Don'tbeintimidatedbytheequationabove.Breakitdown:first,calculate

theaverage;thenloopthroughthearray performingasubtractionand

accumulatingthesum ofthesedifferences;thendividethatsumbyNand

takethesquareroot.

3). Toallowtheusertoenteravariableamountofnumbers,youcanfirstaskfor

thenumberofinputsandacceptthatmanyoryoucanprompttheuserto

enter-1toflagtheendof their list(i.e.loopwhileinputnumber !=-1).

Explanation / Answer

please rate - thanks

any changes needed, let me know

#include <iostream>
#include <math.h>
#include <fstream>
using namespace std;
double mean(double [],int,double&);
double standardd(double[],int, double);
double calc(int, double);
char letter(double);
int main()
{double x[30];
int i=0,j;
double average,sd,sum=0;
do
{cout<<"Enter a number (-9999 when done) ";
cin>>x[i];
i++;
}while(i<30&&x[i-1]!=-9999);
if(x[i-1]==-9999)
   i--;
  
average=mean(x,i,sum);
sd=standardd(x,i,average);
cout<<" The average is "<<average<<" ";
cout<<"The standard deviation is: "<<sd<<" ";
system("pause");
return 0;
}
     
double mean(double x[],int n,double& sum)
{int i;
for(i=0;i<n;i++)
    sum+=x[i];
return (double)sum/n;
}
double calc(double x,double avg)
{double temp;
temp=x-avg;
return temp*temp;
}
double standardd(double x[],int n, double average)
{double mean,sum=0;
int i;
for(i=0;i<n;i++)
    sum+=calc(x[i],average);
mean=sum/n;
return sqrt(mean);
}

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