zepid.calc.utils.risk_ratio¶
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zepid.calc.utils.risk_ratio(a, b, c, d, alpha=0.05)¶ Calculates the risk ratio and confidence intervals from count data.
Risk ratio is calculated from
\[RR = \frac{a}{a + b} / \frac{c}{c + d}\]Risk ratio standard error is
\[SE = \left(\frac{1}{a} - \frac{1}{a + b} + \frac{1}{c} - \frac{1}{c + d}\right)^{\frac{1}{2}}\]Parameters: - a (integer, float) – Count of exposed individuals with outcome
- b (integer, float) – Count of unexposed individuals with outcome
- c (integer, float) – Count of exposed individuals without outcome
- d (integer, float) – Count of unexposed individuals without outcome
- alpha (float, optional) – Alpha value to calculate two-sided Wald confidence intervals. Default is 95% confidence interval
Returns: Tuple of risk ratio, lower CL, upper CL, SE
Return type: tuple
Examples
Estimate the risk ratio, standard error, and confidence intervals
>>> from zepid.calc import risk_ratio >>> rr = risk_ratio(45, 55, 21, 79)
Extracting the estimated risk ratio
>>> rr.point_estimate
Extracting the lower and upper confidence intervals, respectively
>>> rr.lower_bound >>> rr.upper_bound
Extracting the standard error
>>> rr.standard_error