 students now we are going to study wilcox and sign rank test this is also a test to check the mean difference and a non-parametric test wilcox and sign rank test is an alternate 2-peered sample T test which we studied as a parametric test this is its equivalent non-parametric test and when we use this when there is no normality in the data then instead of the paired sample T test we use wilcox and sign rank test and in this we see that there are two observations on one variable before and after of the treatment there is no significant difference as we studied in the paired sample T test and in the experimental designs there is a reading before the intervention and a reading after the intervention and in both the readings there is a significant change as we see in the paired sample T test so if the data is not normally distributed i.e. if the design is an experimental design your research design and you took a reading before and then you did the intervention and then you took a reading so for that we will use wilcox and sign rank test instead of paired sample T test so in this way you will have these three tables first they will have mean scores here the score is 11.2012.43 and in this the negative ranks i.e. the value of your mean rank is 10.4 these 14 cases are like this and the positive ranks are 17 and the mean rank is 20.56 which is above your mean so if we look at the value of z then this is minus 0.1997 and this p value is 0.05 this is about to low 0.04 is low so we will accept this alternate hypothesis that in both the scores there is a statistically significant difference i.e. before and after the readings we have the mean differences statistically significantly differ so we use wilcox and sign rank test when data is normally distributed now and when we can not use paired sample T test