How accurate are radon detectors of a type sold to homeowners? To answer this question, university researchers placed 12 detectors in a chamber that exposed them to 105 picocuries per liter (pCi/l) of radon.16 The detector readings are as follows:
91.9 97.8 111.4 122.3 105.4 95.0
103.8 99.6 96.6 119.3 104.8 101.7
We wonder if the median reading differs signi?cantly from the true value 105.
(a) Graph the data, and comment on skewness and outliers. A rank test is appropriate.
(b) We would like to test hypotheses about the median reading from home radon detectors:
H0: median = 105
Ha: median /= 105
To do this, apply the Wilcoxon signed rank statistic to the differences between the observations and 105. (This is the one-sample version of the test.) What do you conclude?