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Question: just need help with part b...

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Just need help with part (b)

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 263 266 271 272 278 279 281 283 285 (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 Score 300「 Score 300 290 290 280 280 270 270 260 260 250 Year 250 O 1990 1990 2000 2010 20 2010 Ye 2000 2020
Score 300 Score 300 290 290 280 28아 270 270 260 260 Ye 2020 Year 2020 250 1990 2000 2010 1990 2000 2010 (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. What percent of the year-to-year variation in scores is explained by the linear trend? (Round your answer to one decimal place.)
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