MC1-Homework-1

Overview

The purpose of this assignment is to get you started programming in Python. Note that we'll be using Python 2.7 for this course (not Python 3.0). This assignment is structured like many of the homeworks and projects for this course, namely that you are to create a Python function that solves a specific problem. We will call your function and verify that it provides the correct answer.

Task

You should create and test your code in the virtual machine you've installed separately.

Your task for this homework is to write two Python functions: One named stdev_p() that computes the population standard deviation of a list of numbers, and another named stdev_s() that computes the sample standard deviation. We will use the definitions of population and sample standard deviation provided at wikipedia [here]. Specifically the sample stdev should use the "Bessel Correction."

Note that only the functions stdev_s() and stdev_p() will be tested. The main part of the code will not be called or tested. The main code is only there to help you test your code.

You have to write it yourself!

We want you to implement the functions described above using basic Python functions and control flow comments (e.g., while, for, etc.). You are not allowed to import any libraries besides the standard math library.

Template

Here's a template for what your code should look like:

import math as m

# calculate the population standard deviation
def stdev_p(data):
    result = 2.0 # your code goes here
    return result

# calculate the sample standard deviation
def stdev_s(data):
    result = 1.9 # your code goes here
    return result

if __name__ == "__main__":
    test = [2.0, 4.0, 4.0, 4.0, 5.0, 5.0, 7.0, 9.0]
    print "the population stdev is", stdev_p(test)
    print "the sample stdev is", stdev_s(test)

Cut and paste this template into a local file stdev_code.py. Note that the main part of the code tests the two functions. Note also that your main code will not be tested by the auto grading code. Only the specific functions we describe will be called and tested.

You can run your program using the command: python stdev_code.py

Resources and ideas

• Python tutorials
• Python documentation

What to turn in

• Submit your code as a single file stdev_code.py via t-square. It is essential that you use that name exactly.
• Do not submit other files.
• Do not submit zip files.
• Make sure your code file is named correctly.
• Under no circumstance should you submit a word document.

Rubric

• 4 test cases: We will test your code against 4 cases (25% per case). Each case will be deemed "correct" if:
  • 12.5%: stdev_p = reference answer within 10%
  • 12.5%: stdev_s = reference answer within 10%

Required, Allowed & Prohibited

Required:

• Your project must be coded in Python 2.7.x.
• Your code must run successfully on one of the university-provided computers (e.g. buffet02.cc.gatech.edu), or on the provided virtual image.
• Your code must solve a 1000 element list in less than 1 second on one of the university-provided computers.

Allowed:

• You can develop your code on your personal machine, but it must also run successfully on one of the university provided machines or virtual images.
• Your code may import the Python math library.

Prohibited:

• Print statements in your function definitions. No need to print anything.
• Any libraries not listed in the "allowed" section above.
• Any code you did not write yourself.