Question

Given the data and output in the attached file, Construct a 90% confidence interval estimate for the average Sales when Advertising is 25 want a confidence interval. It uses Regressionquizoutput2. Regressionquizoutput1 Regression Statistics Multiple R R Square Adjusted R Square Standard Error N Observations 6 ANOVA df SS MS Regression 1 0.607903685 0.607903685 Residual 4 0.020846315 0.005211579 Total 5 0.62875 Coefficients Standard Error Intercept 1.799069984 0.153403661 GMAT 0.002912113 0.000269635 A graduate school wants to try to predict GPA based on GMAT score. A random sample of 6 students was selected. The data was place into Excel. Partial regression output is shown above.

Answer 1

the first sentence of the question is not a part of the regresion output given , as regression output is for gpa and gmat

we can for the regression equation as

gpa = 1.799 + 0.0029*GMAT

so if we have to predict the GPA , we can put the value of GMAT in the above equation and solve it

lets say gmat = 600

so gpa would be

gpa = 1.799 + 0.0029*600 = 3.53

also , note that confidence interval is given as

point +- z*sd/sqrt(n)

sd/sqrt(n) is also called Standard error

so if were to form 90% CI for GMAT coefficient it would be
z = 1.645 for 90% CI from the z table

0.002912113 +- 1.645*0.000269635
solving for plus and minus signs we get

= 0.00246 and 0.0033