Exercise 4.46.

a. Use Equation (4.1) to determine the sample covariance.
b. Use Equation (4.2) and your answer from part (a) to find the regression equation. Compare your result to that found in the specified exercise.
A collection of observations of a variable y taken at regular intervals over time is called a time series. Economic data and electrical signals are examples of time series. We can think of a time series as providing data points (xi, yi), where xi is the ith observation time and yi is the observed value of y at time xi. If a time series exhibits a linear trend, we can find that trend by determining the regression equation for the data points. We can then use the regression equation for forecasting purposes.

r 0 4 3 1 2 2 3