Question

Implement the following problem as a self-contained python module.

Write a program that continually prompts the user for positive integer values and stores them in a list. You should stop prompting when the user enters a negative integer value.

When the user is done entering values, you should print the list of integers they have provided in sorted order. You should then compute the mean and standard deviation of the values in the list.

Recall that the mean is just the arithmetic average...the sum of all the values divided by the number of values. In mathematics notation we represent the mean with the Greek letter mu, ??.

In statistics, standard deviation is the square root of variance and measures how much, on average, values deviate from the mean. So consider a list of N numbers, with mean mu, ??:

Variance = ??2 = Σ(????−??)2 ?? where Ni is the value at position i in the list. Standard

Deviation = ?? = √??2 = √Variance

You should not be using any built in modules that calculate variance/standard deviation for you, you need to code this on your own.

In order to make your program as modular as possible, however, you should define your own functions to carry out the computation. These functions should be:

• print_sorted – takes a list of integers as input and prints them in sorted order

• compute_mean – takes a list of integers as input and returns the mean (average) of the list

• compute_variance – takes a list of integers as input and returns the variance of the list. (Note that this method can call the computeMean method.)

• compute_standard_dev – takes the variance as input and returns the standard deviation (just the square root of variance).

Answer 1

import math
def print_sorted(A):#prints the list in sorted order
    n = len(A)
    print("Sorted list :",end="")
    for i in range(n):
        for j in range(0, n-i-1):
            if A[j] < A[j+1] :
                A[j], A[j+1] = A[j+1], A[j]
    print(A)
def compute_mean(A):#method to compute and return mean
    sum=0
    for i in A:
        sum=sum+i
    return sum/len(A)
def compute_variance(A):#method to compute variance
    u = compute_mean(A)
    p=0
    for i in A:
        p=p+i*i
    p=p/len(A)
    p=p-(u*u)
    return p
def compute_standard_dev(v):#returns standard deviation
    return math.sqrt(v)
  
l=[]
while(True):#to read user input
    n=int(input("Enter a positive number:(negative number to quit ):"))
    if(n<0):#if negative number is entered
        break
    l=l+[n]#adding it to list
print_sorted(l)
u = compute_mean(l)
print("Mean is :",u)
v = compute_variance(l)
print("Varaiance is :",v)
print("Standard deviation is :",compute_standard_dev(v))

  

output:

>>>
Enter a positive number:(negative number to quit ):1
Enter a positive number:(negative number to quit ):2
Enter a positive number:(negative number to quit ):3
Enter a positive number:(negative number to quit ):4
Enter a positive number:(negative number to quit ):5
Enter a positive number:(negative number to quit ):6
Enter a positive number:(negative number to quit ):7
Enter a positive number:(negative number to quit ):8
Enter a positive number:(negative number to quit ):9
Enter a positive number:(negative number to quit ):-1
Sorted list :[9, 8, 7, 6, 5, 4, 3, 2, 1]
Mean is : 5.0
Varaiance is : 6.66666666667
Standard deviation is : 2.58198889747
>>>