Can chi-squared tests be used for making statements like this or is this an inaccurate analysis of my data?
The majority of the groups (n=9) affected by disease ranged in prevalence from 5.56% to 12.73% with the exception of three groups (groups A, B and C) which produced markedly higher prevalence rates. Chi-squared tests were performed on these however, and it was determined that neither the 39.13% of group A (χ2= 1.08, df=1, P=0.297) nor the 21.05% from group B (χ2= 6.36, df= 1 P=0.12) were statistically significant. The 23.19% from group C (χ2= 59.52, df=1, P=<0.05) was significant thereby marking it out as unique in this assemblage.
Is this acceptable? Or would a more accurate way be to do a chi-square on a 2x9 contingency table? And if it is, how then do you know which group is significantly different from the others?