# Question: Amazon com is an e commerce firm that has shown considerable growth

Amazon.com is an e-commerce firm that has shown considerable growth since its founding in 1995, and its quarterly sales are shown in Table 14.4.4. Their 2009 annual report includes a section titled “Seasonality” that states: “Our business is affected by seasonality, which historically has resulted in higher sales volume during our fourth quarter, which ends December 31.”

a. Construct a time-series plot for this data set. Do you agree that there are seasonal factors present here?

b. Calculate the moving average (using one year of data at a time) for this time series. Construct a time-series plot with both the data and the moving average.

c. Describe any cyclic behavior that you see in the moving average.

d. Find the seasonal index for each quarter. Do these values appear reasonable when you look at the time-series plot of the data?

e. Which is Amazon.com’s best quarter (1, 2, 3, or 4)? On average, how much higher are sales then as compared to a typical quarter during the year?

f. Which is Amazon.com’s worst quarter (1, 2, 3, or 4)? On average, how much lower are sales then as compared to a typical quarter during the year?

g. Find the seasonally adjusted sales corresponding to each of the original sales values. Construct a timeseries plot of this seasonally adjusted series.

h. Describe the behavior of the seasonally adjusted series. In particular, identify any variations in growth rate that are visible over this time period.

QUESTION CONTINUE TO NEXT PAGE…..

a. Construct a time-series plot for this data set. Do you agree that there are seasonal factors present here?

b. Calculate the moving average (using one year of data at a time) for this time series. Construct a time-series plot with both the data and the moving average.

c. Describe any cyclic behavior that you see in the moving average.

d. Find the seasonal index for each quarter. Do these values appear reasonable when you look at the time-series plot of the data?

e. Which is Amazon.com’s best quarter (1, 2, 3, or 4)? On average, how much higher are sales then as compared to a typical quarter during the year?

f. Which is Amazon.com’s worst quarter (1, 2, 3, or 4)? On average, how much lower are sales then as compared to a typical quarter during the year?

g. Find the seasonally adjusted sales corresponding to each of the original sales values. Construct a timeseries plot of this seasonally adjusted series.

h. Describe the behavior of the seasonally adjusted series. In particular, identify any variations in growth rate that are visible over this time period.

QUESTION CONTINUE TO NEXT PAGE…..

## Answer to relevant Questions

Consider PepsiCo’s quarterly net sales as shown in Table 14.4.5. a. Draw a time-series plot for this data set. Describe any trend and seasonal behavior that you see. b. Plot the moving average values on the same graph as ...For each of the following, tell whether it is likely to be stationary or nonstationary and why. a. The price per share of IBM stock, recorded daily. b. The prime rate, recorded weekly. This is the interest rate that banks ...At a meeting, everyone seems to be pleased by the fact that sales increased from $21,791,000 to $22,675,000 from the third to the fourth quarter. Given that the seasonal indices are 1.061 for quarter 3 and 1.180 for quarter ...a. State the hypotheses for the one-way analysis of variance. b. Is the research hypothesis very specific about the nature of any differences? Use multiple regression with indicator variables, instead of one-way ANOVA, to test whether the quality data in Table 15.1.1 show significant differences from one supplier to another. (You may wish to review the material on ...Post your question