A researcher wishes to test the effectiveness of a flu vaccination.Fifty randomly selected people are vaccinated,80 randomly selected people are vaccinated with a placebo,and 300 randomly selected people are not vaccinated.The number in each group who later caught the flu was recorded.The results are shown below. $\begin{array}{r|ccc}
& \text { Vaccinated } & \text { Placebo } & \text { Control } \
\hline \text { Caught the flu } & 7 & 14 & 19 \
\text { Did not catch the flu } & 43 & 66 & 281
\end{array}$
A)Yes.
B)No,because the data are quantitative.
C)No,because the data do not appear to be random.
D)No,because the expected cell frequency condition is violated.
E)No,because the observed counts are too close to the expected counts.

Question

A researcher wishes to test the effectiveness of a flu vaccination.Fifty randomly selected people are vaccinated,80 randomly selected people are vaccinated with a placebo,and 300 randomly selected people are not vaccinated.The number in each group who later caught the flu was recorded.The results are shown below. $\begin{array}{r|ccc} 
& \text { Vaccinated } & \text { Placebo } & \text { Control } \
\hline \text { Caught the flu } & 7 & 14 & 19 \
\text { Did not catch the flu } & 43 & 66 & 281
\end{array}$
A)Yes.
B)No,because the data are quantitative.
C)No,because the data do not appear to be random.
D)No,because the expected cell frequency condition is violated.
E)No,because the observed counts are too close to the expected counts.

Quizplus · Accepted Answer

The expected cell frequency condition is violated because the expected frequency in at least one of the cells is less than 5. In this case, the expected frequency of people who are vaccinated and caught the flu is 2.5. Therefore, the chi-squared test for independence cannot be used.

A Researcher Wishes to Test the Effectiveness of a Flu