Assignment Task: The U.S. consumer price index (CPI or cost of living index), has risen over the years, ????????????(????) = -0.0023???? 3 + 0.1939???? 2 - 0.3962???? + 28.6768 where ???? is time in years since 1960. Note this is based on the average CPI=100 for years 1982-1984 (Source: Bureau of Labor Statistics).
a. Graph this function in an appropriate window, label completely.
b. What is the ????-intercept, and what does this tell you in practical terms?
c. What sales does this model predict in the year 1995? (Note that the actual CPI that year was 152.4.)
d. Do you think this model can be used to predict CPIs into the future, such as in the year 2020? Why or why not?