A least squares regression line is fitted to seasonally adjusted data and is given by:
Calculate the predicted deseasonalised value for time period $15$15, to four decimal places.
If the seasonal index for this period was $69$69%, calculate the true predicted value to four decimal places.
Carry out investigations of phenomena, using the statistical enquiry cycle: A conducting experiments using experimental design principles, conducting surveys, and using existing data sets B finding, using, and assessing appropriate models (including linear regression for bivariate data and additive models for time-series data), seeking explanations, and making predictions C using informed contextual knowledge, exploratory data analysis, and statistical inference D communicating findings and evaluating all stages of the cycle.
Investigate bivariate measurement data