In: Statistics and Probability
8. The following Regression function has been developed to check the relationship between Y-‘Risk of a stroke’ and some other factors;
X1- Age
X2 –Pressure
X3 –Smoker
X4 -Age
Press Consider the following Minitab output and answer the questions.
Risk = - 123 + 1.51 Age + 0.448 Pressure + 8.87 Smoker - 0.00276 AgePress
Predictor Coef SE Coef T P
Constant -123.16 56.94 -2.16 0.047
Age 1.5130 0.5980 2.53 0.021
Pressure 0.4483 0.1291 3.47 0.004
Smoker 8.866 3.074 2.88 0.011
AgePress -0.002756 0.004807 -0.57 0.575
S = 5.881 R-Sq = 87.6% R-Sq(adj) = 84.3%
Analysis of Variance
Source DF SS MS F P
Regression 4 3672.11 918.03 26.54 0.000
Residual Error 15 518.84 34.59
Total 19 4190.95
a) Write the hypotheses of F-test to check the overall relationship between Y and X1,X2,X3 ,X4.
b) What is your conclusion of part (a) ? (Use α =0.05) You need to justify your answer using appropriate value from the output.
c) Write the hypotheses of the t-tests to test whether X1, X2, X3 and Y have a significant regression relationship.
d)What can you say about the significance of the X2 and X4 to the regression equation based on the corresponding t-tests? (Use α =0.05). Please conduct t-test for X2 and X4 separately. Please use appropriate values related to t-test from the above output. Make sure to show all your steps.
e) What can you say about the above regression equation based on the adjusted r2 (R-Sq(adj)) value from the output?