Every few years, the national assessment of educational progress asks a national sample of eighth-graders to perform the same math tasks. the goal is to get an honest picture of progress in math.
suppose these are the last few national mean scores, on a scale of 0 to 500.

year: 1990 1992 1996 2000 2003 2005 2008 2011 2013
score: 265 266 270 271 276 277 279 287 289

(a) make a time plot of the mean scores, by hand. this is just a scatterplot of score against year. there is a slow linear increasing trend.
(b) find the regression line of mean score on time step-by-step.
first, calculate the mean and standard deviation of each variable and their correlation (use a calculator with these functions). then find the equation of the least-squares line from these. (round your answers to two decimal places.) draw the line on your scatterplot.