Oral Contraceptive Use and Ovarian Cancer - Library

More documents

Recommendations

Info

$case studies X\XUnknown Disease in SC\Xunkdis_sc ... - Library$

$Case studies\Xtexarkana\Xtexark.711-505.student.wpd - Library$

$C:\Case studies all\XPBBs in Michigan\Xpbb_s.813-N02.wpd - Library$

$L:\ZVD0\Case Studies\Tampons and Toxic Shock\Xtss ... - Library$

CDC-EIS: OCs and Ovarian Cancer (811-X11) - Participant’s Guide page 6 Question 4: From these data, can you calculate the risk of ovarian cancer among oral contraceptive users? Why or why not? Question 5: Describe the rationale behind using the odds ratio as an estimate of the risk ratio. When is the odds ratio not an appropriate estimate of the risk ratio?
CDC-EIS: OCs and Ovarian Cancer (811-X11) - Participant’s Guide page 7 The investigators used the data in Table 1 and the formulas shown below to calculate an odds ratio and 95% test-based confidence limits. They also calculated a Mantel-Haenszel Chi as a test of statistical significance to evaluate the likelihood that any difference between the observed (calculated) OR and the OR under the null hypothesis could be due to chance. Measure Formula Calculation from Table 1 Odds Ratio (OR) ad (93)(683) OR = = 0.77 bc (959)(86) Expected Value of Cell ‘a’ (E(a)) H 1V E(a)= T 1 (1052)(179) = 103.41 1821 Mantel-Haenszel (MH) Variance H 1 H 0V 1V MH variance= 2 T (T -1) 0 (1052)(769)(179)(1642) = 39.40 2 (1821 ) (1821-1) Mantel-Haenszel Chi* a - E(a) 93 -103.41 X MH = = -1.66 MH variance 39.40 Test-based Confidence Limits (Note: Z values for 2-sided confidence limits are: 90% = 1.645, 95% = 1.96, 99% = 2.58.) (1-(Z/ X MH )) LOWER CL= OR (1 X )) UPPER CL = OR +(Z/ MH 0.77 (1(1.96 / 1.66)) = 0.57 (1 0. (1.96 / 1.66 77 )) 1.05 * The chi is the square root of the more commonly used chi-square. The Mantel-Haenszel chi with one degree of freedom (X MH ) is equivalent to a Z-score and can be used to find the 2-tailed p-value from a table of areas in two tails of the standard normal curve. In this case, p = 0.097.
Page 1 and 2: Centers for Disease Control and Pre
Page 3 and 4: CDC-EIS: OCs and Ovarian Cancer (81
Page 5: CDC-EIS: OCs and Ovarian Cancer (81

Oral Contraceptive Use and Ovarian Cancer - Library

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?