problem 
 1 


The incidence of common colds in a double-blind study involving
279 French Skiers is summarized in the following table.

 center 
 tabular  l|c|c|c 
                  Cold    No Cold   Totals     2-4 
Placebo 	  31	  109	    140        2-4 
Vitamin C	  17	  122	    139        
Totals		  48	  231	    279 
 tabular 
 center 
When testing the null hypothesis that Vitamin C has no therapeutic
value  for treating common cold we obtain (choose one):

 choice 
  , p-value  . Can't reject 
  , p-value  . Can't reject 
  , p-value  . Reject 
  , p-value  . Reject 
  , p-value  . Reject 

 choice 


 longanswer 

Expected table under independence (the null)

 center 
 tabular  l|c|c|c 
                  Cold    No Cold   Totals     2-4 
Placebo 	  24.1	  115.9	    140        2-4 
Vitamin C	  23.9	  115.1	    139        
Totals		  48	  231	    279 
 tabular 
 center 

Therefore:  , and the p-value from the Chi-square
table with 1 degree of freedom is less than 5  so we reject the
null. We conclude that vitamin C shows a significant effect.

 longanswer 
 problem