Consider a claim that 60% of the mice in a region have parasitic infections. We can use an ?² goodness-of-fit test to test whether the proportion is indeed 60%. Consider a study in which we collect a random sample of 50 mice and 37 have infections. Calculate the ?² value, and using the table of critical values shown, what is the conclusion of our test?
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$\begin{array}{c}\chi^{2} \text { critical values }\\\text { for } d f=2\\\begin{array}{ll}\text { Sig. level } & \text { Value } \\\hline 0.05 & 3.84 \\0.025 & 5.02 \\0.01 & 6.63\end{array}\end{array}$

Question

Consider a claim that 60% of the mice in a region have parasitic infections. We can use an ?² goodness-of-fit test to test whether the proportion is indeed 60%. Consider a study in which we collect a random sample of 50 mice and 37 have infections. Calculate the ?² value, and using the table of critical values shown, what is the conclusion of our test?
?

\begin{array}{c}\chi^{2} \text { critical values }\\\text { for } d f=2\\\begin{array}{ll}\text { Sig. level } & \text { Value } \\\hline 0.05 & 3.84 \\0.025 & 5.02 \\0.01 & 6.63\end{array}\end{array}

Quizplus · Accepted Answer

The expected number of infected mice is 30 (60% of 50). The observed number is 37. The chi-square statistic is calculated as $\chi^2 = \frac{(37-30)^2}{30} + \frac{(13-20)^2}{20} = 4.9$. This value is greater than the critical value of 3.84 at the 0.05 significance level, so we reject the null hypothesis, concluding the percentage is not 60%.

Consider a Claim That 60% of the Mice in a Region