Python Puzzles
Simulate a multiple-choice exam where you divide the questions into three probabilities of attaining a correct answer.
- Questions that have a 100% confidence of being correct
- Questions that have a 1/3 confidence of being correct
- Questions that have a 1/4 confidence of being correct
After running 10,000 simulations of the exam, determine the following:
- Average number of correct answers
- Minimum and maximum number of correct answers
- Percentage of the exams where the number of correct answers is over some desired value
- Standard Deviation
In my simulation I choose a 50 question exam where my desired score of 35 was attained 74% of the time.
Here are the results of the print statements from my Python code below.
This Pandas Series shows the number of questions correct on the left and the occurrences on the right.
1,916 exam simulations had 36 correct answers.
Probability of obtaining a score of 35 or greater is 73.83%
The average score is 35.84
The minimum score is 30.00
The maximum score is 45.00
The standard deviation is 2.02
30 6
31 77
32 299
33 867
34 1368
35 1866
36 1916
37 1528
38 1111
39 576
40 260
41 93
42 21
43 10
44 1
45 1Reviewing the bar chart, we can see the data fits a normal distribution.
The mathematical formula to determine the mean is pretty simple. Here we can see the average score will be 36.83, which aligns without simulation.
E(X) = 30 + (1/3) * 10 + (1/4) * 10 = 30 + 3.33 + 2.5 = 36.83
Here is the code I developed in Python.
# import necessary libraries
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd
# define variables for the simulation
desired_score = 35
known_guess = 1
educated_guess = 1/3
random_guess = 1/4
simulations = 10_000
# simulate the exam results using binomial distribution
np_result = np.random.binomial(30, known_guess, simulations)
np_result = np.add(np_result, np.random.binomial(10, educated_guess, simulations))
np_result = np.add(np_result, np.random.binomial(10, random_guess, simulations))
# filter the results to find the probability of obtaining the desired score or greater
filter_arr = np_result >= 35
newarr = np_result[filter_arr]
probability_desired_score = len(newarr)/len(np_result)
# output the results
print('Probability of obtaining a score of ' + str(desired_score) + ' or greater is ' + '{0:.2f}%'.format(probability_desired_score*100))
print('The average score is ' + '{0:.2f}'.format(np.average(np_result)))
print('The minimum score is ' + '{0:.2f}'.format(np.min(np_result)))
print('The maximum score is ' + '{0:.2f}'.format(np.max(np_result)))
print('The standard deviation is ' + '{0:.2f}'.format(np.std(np_result)))
# create a pandas series and plot the distribution
df = pd.Series(np_result)
df = df.value_counts()
print(df.sort_index())
plt.bar(df.index, df.values)
plt.title('Distribution of Correct Answers')
plt.xlabel('Correct Answers')
plt.ylabel('Frequency')
plt.xticks(np.arange(min(df.index), 51, 2))
plt.savefig('guessing-multiple-choice-distribution-answers.png', dpi=300, bbox_inches='tight')
plt.show()