# Statistics: Final

March 2, 2011

*This final is due Sunday, March 6 by 11:00pm. Finals must be submitted via email to the instructor. Submissions must include Excel workbooks, SPSS output files, and a seperate Word document which provides the answers. See below the “more…” link for the full exam.*

**Objective: **We wish to find the factors that determine brain size (MRI_Count). Potential explanations are gender, IQ, weight, and height. A larger MRI_Count denotes a larger brain.

**Addendum**: Please note I modified question 11 due to an error at 1:30 on Wednesday.

- Copy this dataset from the webpage to an Excel worksheet. The gender variable should be placed in column A.
- Recode the “Gender” variable so females are coded as 1 and males as 0. Place the recoded variable, named “Gender2”, in column B. Do not delete any variables during this process.
- Divide weight by height (i.e., weight/height) for a new variable called “Weight_per_inch”.
*Note: Think about why this is needed. Someone may be heavy because they are tall or because they are obese. We need to adjust weight by dividing by height. This gives us the weight (in pounds) per inches.* - In a separate Word document, provide the
*n*-size. - Create a column chart which graphs the number of males and females in the data set. Copy and paste this chart in a separate Word document and summarize the findings. Specifically, tell me the
*number*of males and females and the*percentage*of males and females. - Find the averages and standard deviations for: MRI_Count; FSIQ; VIQ; PIQ; Weight; Height. Provide these answers in a separate Word document.
- Use a pivot table to find the average “MRI_Count” for males and females. Summarize the findings (e.g., just tell me the mean MRI_Count for males and females) in a separate Word document.
- Create a scatterplot showing the relationship between FSIQ and MRI_Count. Show FSIQ on the x-axis and MRI_Count on the y-axis (you may draw a trend line, but don’t show any equations).
*Also*, calculate the correlation coefficient. Describe the relationship you found in a separate Word document. Copy and paste the scatterplot into the document. - Create a scatterplot showing the relationship between Weight_per_inch and MRI_Count. Show Weight_per_inch on the x-axis and MRI_Count on the y_axis (you may draw a trend line, but don’t show any equations).
*Also*, calculate the correlation coefficient. Describe the relationship you found in a separate Word document. Copy and paste the scatterplot into a document. - Import the data into SPSS.
- Calculate an independent-sample t-test between MRI_Count between
**genders**. Describe the results in a separate Word document. Specifically, tell me whether the two variables are related and*how*you arrived at that conclusion. - Run a multiple regression with Gender, FSIQ, and Weight per Inch as independent variables and MRI_Count as the dependent variable.
- Describe the relationship between Gender, FSIQ, and Weight per Inch, including if the relationship is positive or negative and whether it is statistically significant.
- How much of the differences in brain size (MRI_Count) is explained by these three variables?
- What is the predicted MRI_Count for a male, with an FSIQ of 125, and a 72″ tall male who weighs 185 pounds?
- Summarize, in one paragraph, the factors that influence brain size.

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