Management of a home appliance store in Charlotte wants to understand the growth pattern of the monthly sales of DVD units over the past 2 years. Managers have recorded the relevant data in the file P16_44.xlsx.

The question is whether the sales of DVD units have been growing linearly over the past 24 months.

a. Generate a scatterplot for sales versus time.

Comment on the observed behavior of monthly DVD sales at this store.

b. Estimate a simple regression model to explain the variation of monthly DVD sales over the given time period. Interpret the estimated regression coefficients.