Bayesian Seasonality Analysis of Rates When the Population at Risk Is Allowed to Vary

Abstract We present what appears to be the first Bayesian procedure to analyze the seasonal variation of rates from data that generally have small amplitude and small sample size, with a possibly variable population at risk. Such data are pertinent both to the medical and the social sciences, for example. Our procedure is easy to apply and versatile, because it can be used to assess various usual patterns of seasonal variation. To illustrate the application of our procedure, we provide three examples with different seasonal patterns. Based on real data, the examples are enhanced by tables and graphics that elucidate the procedure’s application.