19. Consider the following time series.

t	1	2	3	4	5	6	7
Yt	120	110	100	96	94	92	88

a. Construct a time series plot. What type of pattern exists in the data? b. use simple linear regression analysis to find the parameters for the line that minimizes mSe for this time series. c. What is the forecast for t = 8?

21. The Centers for disease Control and Prevention office on Smoking and Health (oSH) is the lead federal agency responsible for comprehensive tobacco prevention and control. oSH was established in 1965 to reduce the death and disease caused by tobacco use and exposure to secondhand smoke. one of the many responsibilities of the oSH is to collect data on tobacco use. The following data show the percentage of u.S. adults who were users of tobacco for a recent 11-year period (http://www.cdc.gov/tobacco/data_statistics /tables/trends/cig_smoking/index.htm).

Year	Percentage of Adults Who Smoke
1	22.8
2	22.5
3	21.6
4	20.9
5	20.9
6	20.8
7	19.8
8	20.6
9	20.6
10	19.3
11	18.9

a. Construct a time series plot. What type of pattern exists in the data? b. use simple linear regression to find the parameters for the line that minimizes mSe for this time series. c. one of oSH's goals is to cut the percentage of u.S. adults who were users of tobacco to 12% or less within nine years of the last year of these data. does your regression model from part (b) suggest that oSH is on target to meet this goal? if not, use your model from part (b) to estimate the number of years that must pass after these data have been collected before oSH will achieve this goal.