You are conducting a case control study to determine if an association exists be

Question

You are conducting a case control study to determine if an association exists between melanoma and indoor tanning. From a statewide cancer registry, you identify 1,107 people who were diagnosed with melanoma during the last three years. You select 1,500 controls for your study. Through a follow-up survey, you find that 696 of those with melanoma had a history of indoor tanning. 48.2% of the control group reported no exposure to indoor tanning.

Part I: Calculate the odds ratio.

Part II: Interpret your results.

Explanation / Answer

First of all we will make the table-

             Cases                                   Controls

a = 696

                                                b = 1500 -723                          = 777

                                                           c = 1107 – 696 = 411

                                               d = 0.482* 1500

= 723                       

Exposed to indoor tanning

                                                                    Not exposed to indoor tanning

Part I: Now odds ratio = (a/c) / (b/d) = (696/411) / (777/723)

                                                 = 1.69 / 1.07 = 1.58

Part II: Since the odds ratio is greater than 1, it means that there are higher odds of melanoma happening in people exposed to indoor tanning, than in ones not exposed to indoor tanning.

Thanks!

a = 696

                                                b = 1500 -723                          = 777

                                                           c = 1107 – 696 = 411

                                               d = 0.482* 1500

= 723                       

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