Null Hypothesis in every case : No association between exposure and illness

 Rank-ordering the odds ratios

   1.  raw pork:        (3.26)     

  2.  pets:                (1.94)    

  3.  other illness:  (0.63 or 1.58 protective)   

  4.  raw milk:         (1.39)       

  5.  Mexico:           (1.18)

  Analysis of strongest association (raw pork). All expected numbers >5 so use ChiSquare.  

             Σ(O-E)²/E  =  4.06       ChiSq(.05)(1df): 3.84       ........ so reject H₀  (P<0.05)

  Summary: There appears to be an association between handling raw pork and becoming ill. 

  Those who handled raw pork were more than 3 times likely to become ill compared to those

  who did not handle raw pork.  This association is statistically  significant (0.05), and the null

  hypothesis may be rejected.  ChiSq= 4.06,  1df,  P<0.05

 Other associations:

 Pets:                OR: 1.94  weak association.  handling pets increased risk by factor of nearly 2

 Raw milk             OR: 1.39   weak association.  drinking raw milk increased risk by 39%

 Other illness         OR: 0.68  (= 1.58 "protective")   Having another illness lowered risk of yersiniosis to 68% of someone

                     without another illness,  (or: Not having another illness increased risk of yersiniosis by 58%)

 Mexico              OR: 1.18    negligible association.    Visiting Mexico increased risk by 18%