Y = a + bx
The graph and accompanying table shown here display 12
observations of a pair of variables (x, y).

The variables x and y are positively correlated, with a correlation
coefficient of r=0.97.

You estimate the slope of the least squares regression line, y= a + bx,
for these data values to be b = 2. What is the y-intercept, a, of the
least squares regression line? Round your answer to the nearest
tenth.

x3 6 8 9 9 13 | 15 | 18 20 | 21 | 23 | 23
y9 17 15 15 24 29 36 43 | 39 | 46 55