A summer language institute for teachers. A matched pairs study of the effect of a summer language institute on the ability of teachers to comprehend spoken French had these improvements in scores between the pretest and the posttest for 20 teachers:
|
2
|
0
|
6
|
6
|
3
|
3
|
2
|
3
|
-6
|
6
|
|
6
|
6
|
3
|
0
|
1
|
1
|
0
|
2
|
3
|
3
|
We wonder if the median reading differs significantly 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?