In statistics, the standard deviation measures the amount of variation or disper

Question

In statistics, the standard deviation measures the amount of variation or dispersion from the average. It can be calculated using the following formula Where is the standard deviation, x is each value in the data set, is the mean of all values in the data set, and n is the number of values in the data set. For your program you will ask the user for double values. Your program should stop when the user enters -99 when at this point your program will display the mean and the standard deviation from the data set. Last Modified: 10/29/2015 Sample output: Enter a value (or -99 to quit): 3 Enter a value (or -99 to quit): 5 Enter a value (or -99 to quit): 11 Enter a value (or -99 to quit): 14 Enter a value (or -99 to quit): 11 Enter a value (or -99 to quit): -99 The average is 8.8 with a standard deviation of 4.11.

must be progammed by C++

Explanation / Answer

// Example program
#include <iostream>
#include<cmath>
#include<vector>
using namespace std;
int main()
{
    double i;
    vector<double> arr;
    while(1)
    {
        cout<<"Enter a value (or -99 to quit): ";
        cin>>i;
        if(i==-99)
            break;
        arr.push_back(i);
    }
    int len = arr.size();
    double mean=0;
    for(i=0;i<len;i++)
        mean += arr[i];
    mean = mean/len;
    double sd=0;
    for(i=0;i<len;i++)
    {
        double t = (mean-arr[i])*(mean-arr[i]);
        //cout<<t<<' ';
        sd += t;
    }
    //cout<<sd<<' ';
    sd = sqrt(sd/len);
    cout<<"The average is "<<mean<<" with a standard deviation of "<<sd<<' ';
}

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