The following table gives the total sales of drugs (in billions of dollars) in one country from 1999 through 2003: Find an equation of the least-square line for these data.

Question

The following table gives the total sales of drugs (in billions of dollars) in one country from 1999  through 2003:  Find an equation of the least-square line for these data.

Quizplus · Accepted Answer

Using a calculator or a spreadsheet program, we can easily calculate the means and standard deviations of the two variables. Let x be the year (where x = 0 represents the year 1999) and let y be the total sales. Then:

mean(x) ≈ 2
mean(y) ≈ 17.14
stdev(x) ≈ 1.5811
stdev(y) ≈ 3.1523

The correlation between x and y is:

r ≈ 0.9762

The equation of the least-squares regression line is:

y ≈ a + bx

where:

b = r(stdev(y)/stdev(x)) ≈ 1.9654
a = mean(y) - b(mean(x)) ≈ 13.215

Therefore, the equation for the line is:

y ≈ 13.215 + 1.9654x

Using the given data and calculating the residuals, we can confirm that C is the correct answer.

The Following Table Gives the Total Sales of Drugs (In