# Question

The file P12_12.xlsx contains five years of monthly data on sales (number of units sold) for a particular company. The company suspects that except for random noise, its sales are growing by a constant percentage each month and will continue to do so for at least the near future.

a. Explain briefly whether the plot of the series visually supports the company’s suspicion.

b. Fit the appropriate regression model to the data. Report the resulting equation and state explicitly what it says about the percentage growth per month.

c. What are the RMSE and MAPE for the forecast model in part b? In words, what do they measure? Considering their magnitudes, does the model seem to be doing a good job?

d. In words, how does the model make forecasts for future months? Specifically, given the forecast value for the last month in the data set, what simple arithmetic could you use to obtain forecasts for the next few months?

a. Explain briefly whether the plot of the series visually supports the company’s suspicion.

b. Fit the appropriate regression model to the data. Report the resulting equation and state explicitly what it says about the percentage growth per month.

c. What are the RMSE and MAPE for the forecast model in part b? In words, what do they measure? Considering their magnitudes, does the model seem to be doing a good job?

d. In words, how does the model make forecasts for future months? Specifically, given the forecast value for the last month in the data set, what simple arithmetic could you use to obtain forecasts for the next few months?

## Answer to relevant Questions

The file P12_13.xlsx contains quarterly data on GDP. a. Look at a time series plot of GDP. Does it suggest a linear relationship; an exponential relationship?b. Use regression to estimate a linear relationship between GDP ...The file P12_18.xlsx contains the daily closing prices of Chevron stock for a one-year period.a. Use the random walk model to forecast the closing price of this stock on the next trading day.b. You can be about 99.7% certain ...Consider the Consumer Price Index (CPI), which provides the annual percentage change in consumer prices. The data are in the file P02_19.xlsx. a. Find the first six autocorrelations of this time series.b. Use the results of ...The file P12_02.xlsx contains the weekly sales at a local bookstore for each of the past 25 weeks.a. Specify one or more promising auto regression models based on autocorrelations of this time series. Estimate each model ...Consider the airline ticket data in the file S12_01.xlsx. a. Create a time series chart of the data. Based on what you see, which of the exponential smoothing models do you think should be used for forecasting? Why?b. Use ...Post your question

0