Time series analysis of births of children with orofacial clefts

Observation of the dates when children with orofacial clefts were born, gives the impression that they were born in clusters, between which there were intervals of different duration. An analysis was therefore undertaken of the period between 1972 to 1997 when 1112 such children were born. For diagnostic checking of stationarity11Stationary series – a time series {xt} with mean and variance being independent of it.of the time series the Box-Ljung test was used. Since it was found that the time series was stationary, analysis of autocorrelation22Autocorrelation – the internal correlation of the observations in a time series, usually expressed as a function of the time lag between observations.function was performed. The results confirmed the impression that children with clefts are born in clusters, between which there are gaps of different duration. This suggests that the birth of a child with a cleft is not a random and independent event.