Var H X E X Z Note The Roadmap shows the formulas for this statistical test

Var h x e x z note the roadmap shows the formulas for

This preview shows page 19 - 24 out of 24 pages.

Var H X E X Z Note: The “Roadmap” shows the formulas for this statistical test based on setting X = a, the number of exposed cases. As an exercise, compute the test-statistic based on the formulas from the “Roadmap”.
Image of page 19
Harvard TH Chan School of Public Health EPI202 – Epidemiologic Methods II Fall 2016 20 Methods for Count Data Hypothesis Test: Variance of X 00106 0 487 1 122 1 609 71 1 609 71 N 1 N 1 C 1 C T M C where N C 1 C N C 1 C H CID Var H X Var 0 1 1 0 1 0 0 . ) ( , ) ( ) ( ) | ( ) | ( Methods for Count Data Construct and Interpret the Hypothesis Test These data are not very compatible with the state of nature described by the null. If the null were true, we would expect to observe results as extreme or more extreme 6 times per 100,000 iterations of this study. If we were interested in a testing framework, with a pre- specified 2-sided alpha of 0.05, we would reject the null hypothesis and conclude that there is a statistically significant association between catecholamine level at baseline and the 7-year cumulative incidence of CHD (assuming no confounding, no selection bias, no information bias).
Image of page 20
Harvard TH Chan School of Public Health EPI202 – Epidemiologic Methods II Fall 2016 21
Image of page 21
Harvard TH Chan School of Public Health EPI202 – Epidemiologic Methods II Fall 2016 22 95% Confidence interval for CID: These data are consistent with 7-year cumulative incidence differences ranging from 5 to 21% with 95% confidence (assuming no confounding, no selection bias, no information bias) ) 0.209 0.053, ( = 0.001582 1.96 0.131 Methods for Count Data Point estimate for the Cumulative Incidence Ratio There is a 2.5-fold higher 7-year cumulative incidence of CHD among those with high CAT levels compared to those with low levels (assuming no confounding, no selection bias, no information bias). 45 . 2 09 . 0 22 . 0 487 44 122 27 ˆ 0 1 N b N a R I C
Image of page 22
Harvard TH Chan School of Public Health EPI202 – Epidemiologic Methods II Fall 2016 23 Methods for Count Data Variance for ln ( Cumulative Incidence Ratio) ( ln (CIR)) 95% Confidence interval: Let X = ln (CÎR) = ln (2.45) = 0.8959 ar(X) V ˆ 1.96 X 0.0495 = 487 * 44 443 + 122 * 27 95 = N b b - N + N a a - N = C N C - 1 + C N C - 1 = R) I C ( ar V = (X) ar V 0 0 1 1 0 0 0 1 1 1 ˆ ˆ ˆ ˆ ˆ ln ˆ ˆ Methods for Count Data Confidence Interval for Cumulative Incidence Ratio (CIR) 95% Confidence interval for ln (CIR): 95% Confidence interval for (CIR): These data are consistent with cumulative incidence ratios ranging from 1.6 to 3.8 with 95% confidence (assuming no confounding, no selection bias, no information bias) 1.332) (0.4598, = 0.0495 1.96 0.8959 3.79) (1.58, = e = e ) 1.332 0.4598, ( ) ar(X) V 1.96 X ( ˆ
Image of page 23
Harvard TH Chan School of Public Health EPI202 – Epidemiologic Methods II Fall 2016 24 Key Concepts Formulas Person-time (poisson) based methods for use in open and closed cohort studies Methods for case-control studies Count-based (binomial) methods for closed cohort and cross-sectional studies
Image of page 24

You've reached the end of your free preview.

Want to read all 24 pages?

  • Fall '16
  • MURRAY
  • Epidemiology, Statistical hypothesis testing, TH Chan School of Public Health, Harvard TH Chan, TH Chan School

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture