# biostatistics and epidemiology analysis using SPSS

**Question description**

You conduct a study to determine if drinking diet soft drinks is associated with an elevated risk for cancer, specifically bladder cancer or esophageal cancer. You recruit 253 individuals who screen negative for cancer and follow them over a period of 10-years. It turns out that 42 of the study participants reported drinking diet soft drinks on a regular basis (defined as drinking an average of at least 60ozs per week) at the beginning of the study, and therefore were classified as exposed. Using the CROSSTAB functions of SPSS, create a 2x2 table and calculate relevant statistics to answer the following questions.

**Esophageal Cancer:**

1. What is the null hypothesis that you are testing in this study regarding diet soft drinks and esophageal cancer?

2. What is the risk of esophageal cancer among the exposed and among the unexposed?

3. Calculate the risk ratio (RR) for esophageal cancer by hand.

4. What are the risk ratio and 95% confidence interval from the crosstab function of SPSS*?

5. How would you interpret the RR and 95% confidence interval?

6. Calculate the odds ratio (OR) for esophageal cancer by hand.

7. What are the OR and 95% CI from the crosstab function of SPSS?

8. How would you interpret the RR and 95% confidence interval?

9. Calculate the risk difference for esophageal cancer by hand

10. How would you interpret the risk difference?

11. How might you estimate the rate ratio form the 2x2 table? Calculate the rate ratio using this method.

12. What assumptions do you need to make to estimate the rate ratio?

13. How do the risk ratio, odds ratio and rate ratio compare (i.e. are they similar or different)? Why are they exhibiting this pattern?

**Bladder Cancer:**

1. What is the null hypothesis that you are testing in this study regarding diet soft drinks and bladder cancer?

2. What is the risk of bladder cancer among the exposed and among the unexposed?

3. Calculate the risk ratio for bladder cancer by hand.

4. What are the risk ratio and 95% confidence interval from the crosstab function of SPSS*?

5. How would you interpret the RR and 95% confidence interval?

6. Calculate the odds ratio for bladder cancer by hand.

7. What are the OR and 95% CI from the crosstab function of SPSS?

8. How would you interpret the RR and 95% confidence interval?

9. Calculate the risk difference for bladder cancer by hand.

10. How would you interpret the risk difference?

11. How might you estimate the rate ratio form the 2x2 table? Calculate the rate ratio using this method.

12. What assumptions do you need to make to estimate the rate ratio?

13. How do the risk ratio, odds ratio and rate ratio compare (i.e. are they similar or different)? Why are they exhibiting this pattern?

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