Survival of the Fittest...

How I'm surviving stu-vac

I thought I might share with whoever actually reads this the type of questions that are leading me to drink alone.  And this way I can say that blogging is not taking away from my studies.  Clever, eh?

An experiment was designed (Science 120, 12th nove 1954) to investigate whether the smoke of  cigarette papers is a carcinogenic agent of lung tumors.  In this experiment 74 mice were used, of which 38 served as experimental and 36 as control animals.  The experimental mice were placed in the experimental cage and the controls in the control cage of the smoking machine.  This machine was set to smoke108 cigarette papers per day, six days per week for one year.  The environment of the control mice was exactly like that of the experimental animals except for the smoke from the cigarette papers.  At the end of the experiment the animals were sacrificed.  There were 13 tumors in the experimental and 11 in the control mice.  

The author states: "There is a very slight preponderance of tumors in the experimental over the control mice which is not significant by statistical analysis...The results of this experiment indicate that cigarette paper has little or no effect on the generation of lung tumors in albino mice."

Perform the appropriate statistical analysis to check the first of these conclusions.  What is your conclusion from the analysis? Do you agree with the second statement in the author's conclusion?

Did anyone make it to the end of the problem?  Yea, its rough.  Try deciphering that for 6 hours a day, over and over.  It drives a person to drink.  Just in case you're curious, which I doubt you are, that answer to that question goes like this:

There is little to no evidence to reject the null hypothesis that there is a difference in tumor rates in albino mice exposed to smoke from cigarette papers and those exposed to smoke from a smoke machine (x2= .11 with 1df; p=.73).  Of the mice exposed to smoke from the cigarette papers 34% developed tumors, while 31% of the mice exposed to smoke from the smoke machine developed tumors.  The difference is only 3% which does not fit in with the calculated 95% confidence interval of 18% to 25%.