## Question

1. In class , we discussed some issues that might lead to bias in a study, including lack of random selection. Describe a study that suffers from this problem (either one you’ve heard/read about or one you make up). Then describe a way you might change the study to address the problem.

2. Now do the same thing with a study that suffers from lack of random assignment.

Using the data set of maternal ages and birthweights that you created last week, do the

following. Include the appropriate SPSS output. Use full sentences to answer the questions. For questions where you need to report results from the SPSS output , write up the results in proper format, using

sentences to describe the r esults in words, and including the test statistic, df (you can put those in a subscript like I do or in parentheses like Dr. Field does), confidence intervals, and bootstrap information where appropriate.

3. Run a regression with Mother’s Age as the independent variable and Birth Weight as the dependent variable. You can do this using Analyze -> Regression -> Linear.

4. Do you think you would want to assess these data to see if they are normally distributed? Why or why not?

5. Pick at least one appropriate graph f or each variable that you can use to get a sense of whether the data are close to normal, and if there are outliers. Based on the graphs, do you see any problems with the data?

6. Pick a t least one appropriate graph to get a sense of whether birthweight is l nearly related to mother’s age, and if there is heteroscedasticity. Based on the graphs, do you see any problems with the data?

7. Calculate the z -scores for skewness and kurtosis for both variables. Include the SPSS output that you used to get the numbers you need to do calculate the z -scores (you don’t

need to include ALL the SPSS output, just the part that is relevant to calculating z-scores for these statistics) and show the calculation. Write up your results in full sentences, including the relevant statistics.

8. Conduct an d interpret a Shapiro-Wilk test for each variable . Include the relevant SPSS output. Report on what the output means; be sure to use full sentences and include the relevant statistics.

9. Re -run the regression analysis using the bootstrap command, taking 1,000 samples. Report the estimate of the regression coefficient and the 95% confidence interval , using full

sentences and the relevant statistics . How do these compare with the estimate from the non - bootstrapped analysis?

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