Incidence rate ratio

$$IRR = IR_e/IR_u$$ with \(Var(\log IRR) = 1/a + 1/b\) from the case counts. The variance needs counts, not rates, so the interval is returned only when the counts are supplied.

Usage

Incrtio(
  IR_e,
  IR_u,
  cases_exposed = NULL,
  cases_unexposed = NULL,
  confidence = 0.95
)

Arguments

IR_e, IR_u

Incidence rates in the exposed and unexposed.

cases_exposed, cases_unexposed

Optional case counts.

confidence

One of 0.90, 0.95, 0.99.

Value

Named list with estimate, ln_estimate, se_ln, ci_lower, ci_upper, confidence, method.

References

Rothman & Greenland, Modern Epidemiology.

Examples

Incrtio(0.02, 0.01, cases_exposed = 20, cases_unexposed = 10)
#> $estimate
#> [1] 2
#> 
#> $ln_estimate
#> [1] 0.6931472
#> 
#> $se_ln
#> [1] 0.3872983
#> 
#> $ci_lower
#> [1] 0.9361837
#> 
#> $ci_upper
#> [1] 4.272666
#> 
#> $confidence
#> [1] 0.95
#> 
#> $method
#> [1] "incidence rate ratio (Rothman & Greenland)"
#>