The average life expectancy in the United States, L, has been rising steadily over the past few decades, as shown in the table below. Let t be the number of years since 1920, (so t=0 represents the year 1920).
| Year |
1920 |
1930 |
1940 |
1950 |
1960 |
1970 |
1980 |
1990 |
| Life expectancy |
55.4 |
57.1 |
61.4 |
63.4 |
66.3 |
69.7 |
71.2 |
75 |
(a) Find the equation of the regression line.
Average life expectancy, L(t)= .
Note: this is a function of t (not x).
(b) Estimate the average life expectancy in the United States in the year 1956 according to the linear model in part (a).
Average life expectancy in 1956?
The life expectancy in 2008 was calculated by the US Census Bureau to be 78.
What life expectancy does your linear model predict in 2008?