Abstract
The number and amount of external liquid preparations made in Shinshu University Hospital were studied by time series analysis. Time was represented by t (eg, t=1 stands for April 1974) and the analysis was made by the following equation model: Y (t) =T (t) +S (t) +I (t)[Y: original data, S (t): trend variation, I (t): residual variation]. It was found that 9 and 12 month periodicity was observed by the correlogram of the number of external liquid preparations, and 12 month periodicity by that of the amount. The switching point was estimated by Quandt's method. The regression polygonal lines were proved useful since the residuals were assured at random by Durbin-Watson ratio. The number and amount of external liquid preparations decreased in January and increased in the Summer months and in December. Inconsistent coefficient by Theil was 0.03 when seasonal variation was modified.