1. EPI 811 WORK GROUP EXERCISE #1 Team Honey Badgers Alex Montoye Kellie Mayfield Michele Fritz Anton Frattaroli

2. “n11 n12 n21 n22” Notation Corresponding indices: n11 – Exposed Cases n12 – Unexposed Cases n21 – Exposed Controls/Non-Cases n22 – Unexposed Controls/Non-Cases Given: Notation: n11n12n21n22 7033022374

3. The ‘cci’ Command Part of the “Tables for epidemiologists” suite of commands (epitab), the case-control immediate analysis command takes n11 n12 n21 n22 notation parameters. “Point estimates and confidence intervals for the odds ratio are calculated, along with attributable or prevented fractions for the exposed and total population.” Example output using the HCV data from the previous slide:

4. ‘cci’ Command Options Several options are available for approximating the odds ratio and attributable fractions for the exposed. ‘exact’ – recommended when least frequent cell has < 1000 cases. Approximation default. Necessary for small samples; conservative for large. ‘Woolf’ – uses Taylor expansions. ‘Cornfield’ – uses the natural logarithm iteratively. Longer time to compute. ‘tb’ – test based approximation is not recommended for research work. The ‘level’ option allows for different C.I. alpha levels and can be used in conjunction with the approximation options.

5. The ‘csi’ Command Also a member of epitab, the cohort study immediate analysis command takes n11 n12 n21 n22 notation parameters. “It calculates point estimates and confidence intervals for the risk difference, risk ratio, and (optionally) the odds ratio, along with attributable or prevented fractions for the exposed and total population.” Example output using the HCV data:

6. ‘csi’ Command Options Deceptively similar to the ‘cci’ command options. The ‘or’ option gives the odds ratio with a Cornfield approximated C.I. ‘exact’ approximation is the default. *The ‘woolf’ option only applies when the ‘or’ option is in place.

7. Thanks. Questions? Sources: HCV data obtained from the exercise handout by Jim Anthony Screenshots from Stata licensed on Michigan State University equipment. Supplemental information from the documentation section of stata.com