One of the goals of the Edinburgh Artery Study was to investigate the risk factors for peripheral arterial disease among persons 55 to 74 years of age. You wish to compare mean LDL cholesterol levels, measured in mmol/liter, among four different populations of subjects: patients with intermittent claudication or interruptions in movement, those with major asymptomatic diseases, those with minor asympotommatic disease, and those with no evidence of disease at all. Summary statistics are below:
Intermittent Claudication n= 73, mean = 6.22; sd = 1.62
Major asymptomatic disease n=105, mean =5.81, sd =1.43
Minor Asymptomatic Disease n=240, mean =5.77, sd=1.24
No disease n=1080, mean = 5.47; sd =1.31
a. Test the null hypothesis that the mean LDL cholesterol levels are the same for each of the four populations. What are the degrees of freedom associated with this test.
Using ANOVA (by hand!!!) I get a test statistic of 10.90 (ndf=3; ddf=1494) . probability = .000001
b. What do you conclude? less than .05 so null hypothesis is rejected?