The values in the
D 7 series are subtracted from (additive model) or divided into (multiplicative case) the values in
C 19 (or
B 1 if no adjustment for trading-day variation is applied). Then an analysis of variance by month (or quarter) is performed on this series, in order to test for the presence of stable significant seasonality. For more information, see
X-11 Census Method II Seasonal Adjustment .