Biostatistics

I have this homework in biostatistics and it is due on Friday

1. The SAS dataset “112211” on blackboard gives the systolic blood pressure (SBP), body size (QUET), age (AGE), and smoking history (SMK = 0 if a nonsmoker, SMK =

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if a current or previous smoker) for a hypothetical sample of 32 white males over 40 years old from the town of Angina. (QUET stands for “quetelet index,” a measure of size defined by QUET = 100 (weight/height2).)

a. On the accompanying scatter plot for QUET vs. AGE, sketch by eye a line that fits the data reasonably well. Comment on the relationship described.

b. (1)

Determine the least-squares estimates of the slope ( 1) and intercept ( 0) for the

straight-line regression of QUET (Y) on AGE (X).

· (2)  Sketch the estimated regression line on the scatter diagram in part (a) involving QUET and 
AGE. Compare this new line with the line you drew in part (a). 


· (3)  Test the null hypothesis of zero slope; be sure to interpret the result. 


· (4)  Based on your test in part (b)(3), would you conclude that body size increases 


as age increases? Explain your answer.

· (5)  Obtain a 95% confidence interval for 1. In1terpret your result. 


· (6)  Would you reject the null hypothesis H0: = 0 in part (b)(3) based on the confidence 


interval that you calculated in part (b)(5)? Explain.
(7) Use SAS to find and draw 95% confidence bands and prediction bands with fitted

line on the scatter plot. (Must enable html output option in SAS: Tools->Options ->Preferences->Results->Check “Create HTML”.)

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(8) Find the 99% confidence interval and prediction interval for an individual with AGE = 45 from SAS output. Interpret your answer.
(9) Determine r and r2, and interpret your results, respectively.
(10) Test H0: ρ = 0 versus H1: ρ ≠ 0 at α = .01, respectively. (Calculate by hand).