zepid.calc.utils.incidence_rate_ratio¶
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zepid.calc.utils.incidence_rate_ratio(a, c, t1, t2, alpha=0.05)¶ Calculates the incidence rate ratio and confidence intervals from count data
Incidence rate ratio is calculated from
\[IR = \frac{a}{t_1} / \frac{c}{t_2}\]Incidence rate ratio standard error is
\[SE = \left(\frac{1}{a} + \frac{1}{c}\right)^{\frac{1}{2}}\]Parameters: - a (integer, float) – Count of exposed individuals with outcome
- c (integer, float) – Count of unexposed individuals with outcome
- t1 (integer, float) – Person-time contributed by those who were exposed
- t2 (integer, float) – Person-time contributed by those who were unexposed
- alpha (float, optional) – Alpha value to calculate two-sided Wald confidence intervals. Default is 95% confidence interval
Returns: Tuple of IR, lower CL, upper CL, SE
Return type: tuple
Examples
Estimate the incidence rate ratio, standard error, and confidence intervals
>>> from zepid.calc import incidence_rate_ratio >>> ir = incidence_rate_ratio(45, 21, 109, 158)
Extracting the estimated incidence rate ratio
>>> ir.point_estimate
Extracting the lower and upper confidence intervals, respectively
>>> ir.lower_bound >>> ir.upper_bound
Extracting the standard error
>>> ir.standard_error