Some time series are better fit by a curved trend line rather than a straight line.
Our text asks us to calculate an exponential trend equation of Sales versus Time. See page 716 of our text for another statement of the form of the equation. Sales would be the dependent variable and Time would be the independent variable for a linear trend model but for an exponential trend model we must first use the logarithm of Sales as the dependent variable data for the first step of the process of developing the exponential trend equation. Enter the Sales data and the Time period data into Statistix and click Data on the Menu Bar and then highlight Transformations on the drop down menu. Our objective is to have Statistix calculate the natural logarithm of the dependent variable Sales data.