SPSS Output Files

General Directions: This is a take-home exam. You may use books, notes, calculators, and computer software in completing the questions. Please do not hand in the SPSS output files-place your answers in the order they appear on the exam. Please do not delete the questions. All questions are of equal point value.
• Make sure you discuss your results in your own words that explain what the results mean. Explain your rationale for your answer. Simply stating a result is not enough.

• Your answer must include calculations of statistics or portions of statistical computer output that provide relevant statistics. All the statistics provided must be discussed in the accompanying narrative, so if the computer software provides statistics that will not be discussed these should be deleted. Narrative explaining graphs and statistical computations should be placed alongside or immediately before or after each graph or statistical table. It is unacceptable to have all the graphs and statistics grouped together separate from the narrative.
Direct all questions to Prof. Kim (dhkim@wayne.edu)– no other consultants are permitted. Sign the statement below.
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Part I. Using the Freshman.sav data, answer the following questions:

SPSS Data Code:
SATV = verbal score on the SAT
SATM = mathematical score on the SAT
GPA = grade point average
Gender = (1=female) (2=male)
RACE = (1=White/non-Hispanic) (2=African American) (3=Other)

1. Using what you have learned about measures of central tendency and variability, describe the participants in the sample. What is the demographic characteristic of the sample? (e.g., % of male, female, race groups, etc.) What are the mean and standard deviation for SATV, SATM, and GPA?
2. Create a histogram for SATV. Interpret the graph and report what they tell you about the distribution of the variable. Are there any outliers? Are the data normally distributed?
3. Are there differences between males and females on SATM? Create a table that reports means and standard deviations for females and males on SATM. (Hint: Split the file; don’t forget to turn off the split file command before you run other analyses)
4. Are there relationships among SATV, SATM, and GPA? Report Pearson correlation coefficients r. Explain the basis for your answer. For example, is it a strong, moderate, or week relationship? Positive or negative?
5. Produce a scatterplot that depicts the relationship between GPA and SATM.
6. Find the regression equation predicting GPA from SATM. Write out the equation for the regression line.
7. If Mike had a SATM of 640, what would be the predicted GPA? (Note: Predictions in a regression model exclude the error term, estimating the expected value of Y based on the independent variables without accounting for randomness or errors.)

Part II. Consider the following example and refer to it when answering questions 8-10.
Construction companies who bid for road construction work need to offer bids that are low enough to win the contract, but high enough to maximize company profits. A consultant for the
Build More Construction Company attempted to develop a model to predict the price of winning bids. The consultant used two predictor variables: the cost estimate provided by the Department of Transportation engineer and the number of work days required to do the job, as estimated by an independent engineer. Some analyses are presented below. Both the winning bid and the estimated price are given in $1,000s.

8. Write the specific model equation (with numbers) that can be used to predict the winning
   contract cost from the estimated cost and the number of work days required.
9. Interpret the R-square of .974.
10. If you were asked to eliminate one predictor variable from the prediction equation, which one would you choose? Why?