AMS 315
Data Analysis, Fall 2018
First Computing Assignment
The first report is due on Thursday, November 1st but can be submitted without penalty by
November 6th. This report is worth 60 examination points. Please remember that there is a
second project coming, so that you should finish the first project as soon as possible. P lease
submit your project via e-mail as instructed on the Class Blackboard. Detailed submission
information is online.
For the first project, there are two parts: A and B. You should use a total of three files.
Two of the files are for part A, and one file is for part B.
For part A, each file will contain a column for subject ID and a column for either the
dependent variable value or the independent variable value. First, you are expected to sort the
two files by subject ID and merge them. You should not just use “cut and paste” to merge your
data. Second, you are expected to deal with missing data. Your report should contain the count of
the number of subject IDs that had at least one independent variable value or dependent variable
value. It should also include the count of the number of subject IDs that had an independent
variable. There are a number of missing data procedures. Often a statistical package has
imputation algorithms in the software. For example, R has 5 different algorithms available. You
may choose any algorithm except for listwise deletion. Specify your choice in your report. Often,
the choice of imputation method has little effect on the results if the fraction of missing data is 30%
or less. Then, you should use the statistical package of your choice to find the fitted linear model.
The data file for part B will contain one line for each subject ID. The line will contain the
subject ID, the value of the independent variable, and the value of the dependent variable. A
transformation of either IV or DV or both may be required. You should read the text for
suggestions on fitting a model. A lack of fit (LOF) test should be applied if there are repeated
values in the data sets. It is your group’s responsibility to find repeated (or near repeated)
independent variable values. That is, your group should bin near repeated data into one level. For
example, suppose that and . While there are
not exactly repeated x values, your group could bin these points into one group of nearly
repeated points. That is, choose the average x-value as the value of x after binning. Then your
binned data would be and . Then perform. a
LOF test on the data set after binning all near repeated values.
You must submit a one-page report on Problem A and a one-page report on Problem B. Each
report should have four sections. The introduction should contain a statement of the problem and
the objective of the paper. This part is easy: your problem is to recover the function that was
used to generate the dependent variable value based on the value of the independent variable.
The data you receive will be generated by a simulation program. The second section should
describe your methodology. Specifically, how the files were merged, the program used to
perform. the statistical analysis, whether you used linear regression and additional procedures
such as a lack of fit test, how much missing data was present in the data, and the procedure for
dealing with missing data. The third section should contain your results: what fraction of the
variation of the dependent variable was explained, the analysis of variance table, the fitted
function, confidence intervals for slope and test of the null hypothesis that the slope was zero.
The fourth section should be conclusions and discussion. This section should focus on “big
picture” issues. Was there an association between the variables? How important was it? That is,
what was the r-squared value. What is your fitted function? You may submit a longer appendix
of computer work and programs.
Important note:
Simply submitting your computer output is not acceptable and will receive a grade of 0. You
must submit a formal report to begin to get non-zero credit.
Example Report
Here is a sample report. Keep in mind, this is just a general idea of what should the first project
looks like. You must not copy and paste it to submit as your report with the values of the
numbers changed. Such activity is plagiarism and you will receive a grade of 0.
Introduction
The objective is to find the model describing the data in Problem A. A simulation program
using an unknown linear function was used to generate the data.
Methodology
In order to solve problem A, we used the statistics package SPSS and Microsoft Excel
spreadsheet program. The original data files were supplied with two data sheets in Excel. One
data sheet had the ID of an observation and its associated independent variable value, and the
other had the ID and associated dependent variable value. The independent variable data file had
a total of 710 independent variable values with ID# ranging from 1 to 729. The dependent
variable value had a total of 690 dependent variable values with ID # ranging from 1 to 730. We
first sorted data in both files in ascending ID# order and then used Excel to merge the files. We
next used listwise deletion to remove 40 entries that were missing either the independent variable
value or the dependent variable value. Finally, we merged the two files into one file with three
columns: ID, IV and DV. There were 670 entries with both values, with ID# ranging from 1 to
729. The data was then imported into SPSS. We assume linear regression for our data, but in
order to find a better fit, we also transformed dependent variable into DV^2, Sqrt(DV) and
independent variables into IV^2, Sqrt(IV), 1/IV, and ln(IV).
Results
The fitted function for the model Y= B+B1 X was DV=20.966IV+2123.719 with 99.9%
fraction of variance was explained. The 95% confidence interval for the slope was [20.914 ,
21.019]. The 95% confidence interval for the intercept was [2068.988 , 2178.450]. The analysis
of variance table is shown below and the association between the independent variable and
dependent variable was highly significant (p=0.000).
Table 1
Analysis of Variance Table
DV regressed on IV
(n=670)
ANOVAa
Model Sum of Squares Df Mean Square F Sig.
1
Regression 25021381100.435 1 25021381100.435 617186.738 .000
b
Residual 27081402.664 668 40541.022
Total 25048462503.099 669
a. Dependent Variable: DV
b. Predictors: (Constant), IV
Conclusion
For problem A, the association between independent variables and dependent variables
was highly significant (p=0.000), with 99.9% of the dependent variable variationexplained. The
plot of residual versus predicted value confirmed the validity of this model.
Note: For question B, please report transformation you have performed and the model in
transformed format.
End of Report