YOUNG INDIA FELLOWSHIP Statistics Course Group Project Members : Abhishek Chopra Adhiraj Sarmah, Kshitij Garg Mahesh Jakhotia Tulasi Prasad Chaudhary 7/25/2011 The group project is based on real case study taken from the Atlanta primary school test papers. The growing pressure among the teachers to improve the test performance of their classes has resulted in malpractices. We have to find out the methodologies to find out the fraud if done in the following case.
The group project is based on real case study taken from the Atlanta primary school test papers. The growing pressure among the teachers to improve the test performance of their classes has resulted in malpractices. We have to find out the methodologies to find out the fraud if done in the following case.
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YOUNG INDIA FELLOWSHIP
Statistics Course Group Project
Members :
Abhishek Chopra
Adhiraj Sarmah,
Kshitij Garg
Mahesh Jakhotia
Tulasi Prasad Chaudhary
7/25/2011
The group project is based on real case study taken from the Atlanta primary school test papers. The growing pressure among the teachers to improve the test performance of their classes has resulted in malpractices. We have to find out the methodologies to find out the fraud if done in the following case.
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Contents
1) Problem Statement 2
2) Logical Analysis 2-4
3) Inference 4
4) Our Interpretation of the Cheating Process 4
5) Statistical Approaches 5
6) ANOVA 5
7) Pictorial Method 8
8) The Wincoxon Rank Sum Test 9
9) Appendix
a. Table A.1 : Division of questions into groups based
on the approach 1 used in ANOVA test 9
b. Table A.2 : Class Results 10
c. Table A.3: Class B Results 11
d. Table A.5 : Class A Results 12
e. Table A.5 : Class B Results 13
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GROUP PROJECT STATISTICS – FRAUD DETECTION
Problem Statement: We have been given 2 sets of data of 2 different classrooms and we are required to
strategize and analyze to eventually determine whether there was a teacher fraud in one or both of the
classrooms.
There can be 4 different scenarios:
1) Both A & B data have been tampered.
2) Both A & B data have not been tampered.
3) A is Fraud, B is Not
4) B is Fraud, A is Not
We have summarized our thought processes in the following document and demonstrated them through the
help of excel sheets attached in the folder. We have used various approaches to derive the solution. Each
and every methodology has its own assumptions and its own pros & cons.
Logical Analysis:
STEP – 1: We calculate the total number of correct answers for every question in both the classes.
Since we took a student wise-question wise analysis and assign a correct score with the value „1‟, it
also shows the total number of students who got each question correctly for both the classes
STEP -2: We then find the Total Number of correct answers of the entire class and divide it by the
total number of students to arrive at the average mean number of correct answers per student for or
both the classes.
STEP – 3: We take the analysis of STEP -2 and then plot line-graphs for both the classes with
Questions on the X-Axis and Class Performance on the Y-Axis. The analysis of this will provide a
broad perspective on whether there is any evidence of fraud or not.
# We found that in Class – A, Questions 30 to Questions 36 clearly show an anomaly.
STEP-4: We decided to focus on the anomaly region. We analyzed the questions 30-36 and tried to
see if there were any abnormal patterns in them for both the classes.
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# There was very clearly a pattern of answers of exact and uniform correct answers to questions 30-
36 for class A for particular 16 students, which wasn‟t so in Class B.
STEP – 5: We calculated the Average score (i.e. Average no. of correct answers) for each of these
16 students in class A which included questions 30-36. We then found the mean score of these 16
students = 46%.
For Class B, The mean score of all the students is: 38%
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STEP – 6: We calculated the Average score (ie. Average no. of correct answers) for each of these
16 students in class A EXCLUDING the questions 30-36. We then found the mean score the 16
students of Class A, the mean DECREASED to 42% (ie. A decrease of 4%)
For Class B, The mean score of all the students INCREASED to 40%. (ie. An increase of 2%)
INFERENCE: Therefore we can say that the set of questions 30 to 36, show reasonable proof
to believe that some form of cheating/tampering was done in respect to these questions.
Our interpretation of the Cheating Process
1) From questions 30 to 36, the graphs present a consistent growth for 16 students from the other
students from the average growth visually, which can be summed up to 16 x 6 questions, which is
equal to 96 questions that have been probably tampered with.
2) The reasons to choose that particular set of questions (from 30 to 36) could be
a) Since it is given that the level of difficulty increases with the questions it is logical to assume
that more students would get correct answers for the first half of the questions compared to the
second half, because the difficulty level would be low at the beginning. In the same manner, the
second half of the question would be expected to show lesser correct answers as the difficulty
would be higher.
b) So it would be logically smart on the teachers part to attempt to tamper/cheat in the second half
of the questions, since most of the students would be expected to get the correct answers in the
first half. Even in the second half, it would be smarter to avoid tampering with the last few
questions since they are the most difficult, and an increased number of correct answers for those
questions will immediately be easily exposed to detection. So it would be logical to choose
questions from somewhere within the beginning of second half and significantly before the last
few questions.
3) A set of questions which are consecutively chosen for editing also eases the time factor required to
edit the answers manually, which talks about the limited time available to an invigilator or a teacher
generally. And 96 questions is a good number of questions to change the entire average of the class
performance to a significant level which is an increased level of 4 % as we later found from our
analysis..
Statistical Approaches used:
1) Anova Method: Initially we divided the classes into groups and applied anova to see if the groups
have the same distribution or not. If one of the groups did not have the same distribution we could
conclude that the data of that group was tampered as it disturbed the distribution of the whole class.
We used two approaches to divide into groups. Later on we used the Tukey Method to find out the
groups which had a deviated mean.
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2) Pictorial distribution: A graph was plotted with the questions on the X axis and the class
performance on the Y Axis. When we analyzed the class A graph we found out that between the
questions 30-36 the plot was flat and the results were higher than the performances in the other
questions. We can conclude on a pictorial basis that fraud has been done in these questions.
3) The Wilcoxon Rank Sum Test: If we want to use the samples without considering the normal
assumptions we can use the Rank Sum approach (used for non-normal distribution) discussed in
section 9.2 of the text book. Since the other tests are based on a lot of mathematical assumptions
which are not satisfied by the given data, we can use this approach which requires weaker
mathematical assumptions.
Approach 1 : ANOVA Approach
To compare the means and distributions of various groups, ANOVA is preferred to multiple “t-tests” as
ANOVA leads to a single test statistic for comparing all the means, so the overall risk of type-I error can
be controlled. If we ran many t tests, each at a given alpha level, we couldn‟t know what the overall risk of
a type 1 error is. Certainly the more tests one runs, the greater the risk of a false positive conclusion
somewhere among the tests.
Initially we divided the groups of class A according to the toughness level of the questions. The toughness
level was divided according to the area of right answers answered by the students. For example if the total
number of questions answered by the group is 445. We divided the group into eight groups by classifying
them in to equal areas of (445/8=56). The cumulative sum of total scores in each group is 56.
The data was divided into eight groups. The grouping has been shown in appendix section Table A.1
.Anova test was applied on the above groups to find out if the means of the groups was same or different.
Test Hypothesis
Ho : u1= u2=……u8
Ha : Means are not the same(Thus showing that one or more of the groups have been tampered which
resulted in the varying of its mean from the other groups)