{"id":602,"date":"2015-07-20T09:20:20","date_gmt":"2015-07-20T13:20:20","guid":{"rendered":"http:\/\/sites.berry.edu\/vbissonnette\/?page_id=602"},"modified":"2016-06-24T07:52:15","modified_gmt":"2016-06-24T11:52:15","slug":"signed-ranks-test","status":"publish","type":"page","link":"https:\/\/sites.berry.edu\/vbissonnette\/index\/stats-homework\/documentation\/signed-ranks-test\/","title":{"rendered":"Signed-Ranks Test"},"content":{"rendered":"

Example homework problem:<\/h3>\n

Twelve people completed a difficult hand-eye coordination task twice: once in a quiet room, and once in the same room while loud rock-and-roll music was being played. The order in which subjects experienced these conditions was counterbalanced: half performed in the quiet environment first, half performed in the loud environment first.<\/p>\n

The researcher measured the number of errors committed by the participant while performing. Thus, the lower the score, the better the performance. Here are the results:<\/p>\n\n\n\n\n\n
Participant:<\/td>\n1<\/td>\n2<\/td>\n3<\/td>\n4<\/td>\n5<\/td>\n6<\/td>\n7<\/td>\n8<\/td>\n9<\/td>\n10<\/td>\n11<\/td>\n12<\/td>\n<\/tr>\n
Quiet Environment:<\/td>\n14<\/td>\n21<\/td>\n24<\/td>\n16<\/td>\n18<\/td>\n20<\/td>\n15<\/td>\n20<\/td>\n17<\/td>\n16<\/td>\n19<\/td>\n12<\/td>\n<\/tr>\n
Loud Environment:<\/td>\n21<\/td>\n22<\/td>\n21<\/td>\n19<\/td>\n18<\/td>\n25<\/td>\n17<\/td>\n18<\/td>\n21<\/td>\n24<\/td>\n21<\/td>\n15<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Was there a significant difference in performance between the two treatment conditions (alpha = .05)?<\/p>\n

Note that these are the same data that we worked with when you were working with the dependent t<\/i> test procedure<\/a>. This will allow you to compare and contrast the results of the two procedures.<\/p>\n

\n

Enter these data into the first two columns of Stats Homework’s\u00a0<\/i>data manager and rename the variables. Your screen should look like this:<\/p>\n

\"dttest3\"<\/a><\/p>\n

Make sure to double-check and save your data. To conduct your analysis,\u00a0 pull down the Analyze<\/b> menu, choose Non-Parametric Tests<\/b>,\u00a0and then choose Wilcoxon Signed Ranks Test<\/b>.<\/p>\n

Before we look at the output produced by this procedure, let’s take a look at the variables that have been created by it and written back into your data:<\/p>\n

\"srank3\"<\/a><\/p>\n

Note that Stats Homework<\/i> has computed the difference between each pair of scores (Diff Score). It then ranked each of the non-zero differences from 1 to 11. Finally, it assigned a positive sign to the ranks of positive differences and a negative sign to the ranks of negative differences (S_Rank). These scores then are the signed ranks<\/u> that are used in this test. Here is the output from the analysis:<\/p>\n

\"srank2\"<\/a><\/p>\n

The first table presents the sums of the signed ranks: the sum of the positively-signed ranks and the sum of the negatively-signed ranks.<\/p>\n

Exact Test<\/b>. This table includes the test statistic and an exact test of their significance level.<\/p>\n