Answer
Let us make the hypothesis that the techniques adopted by both the groups are
similar and the data is similar also.
Expected frequencies are
investigator Income groups total
poor middle rich
A 120 60 20 200
B 180 90 30 300
Total 300 150 50 500
λ
2
=∑
=
Degree of freedom = (3-1)(2-1)=2
Table value of 2 λ
2
for 2 degree of freedom at 5% level of significance is 5.991. Since
the calculated value is bigger than the table value, we conclude the rejection of null
hypothesis at 5% level of significance. Technique adopted by one of two groups in
data collection is defective.