Categorical data analysis (likert scale)

[Daniela Rozzi]

Hello everyone, I'm working with categorical data on likert scale (4 scales) referred to the same sample of people (70 obs.) at Time0 and Time1. I have, for exemple, 9 different questions on a particular theme at the two different times.
It is the first time I work with this kind of data. I have already computed the frenquencies and represented them in a bar graph, someone could suggest me some index to calculate in order to show the differences between the ditributions in the two periods?
If I verify that my data are normally distributed can I use a paired t-test? It is statistically correct given that data are not continuos?
Some other ideas?

Thank you in advance.

[Fei Wang]

I wouldn't treat your variables as normally distributed. You may use -signrank- to test for equality of distributions for matched data.

[Daniela Rozzi]

I tried to use signrank and in the attachment Signrank.pdf you can find the result.
Could you help me to interpret them?

[Fei Wang]

We are not able to reject that the distribution of the variable at Time 0 is identical to that at Time 1.

[Daniela Rozzi]

Just to be sure to have understood: we are not able to reject that the distribution of the variable at Time 0 is identical to that at Time 1 because the value 'Prob > |z| = 0.6642' is >0.05?

[Fei Wang]

Just to be sure to have understood: we are not able to reject that the distribution of the variable at Time 0 is identical to that at Time 1 because the value 'Prob > |z| = 0.6642' is >0.05?

Exactly.

[Daniela Rozzi]

Given that I have to analyse a survey with 6 different groups of questions, each measuring a different ability (in each group I have from 6 to 9 questions). The questions are on a Likert scale from 1 to 4 (1 a lot, 2 enough, 3 a little, 4 not at all), if I would like to evaluate, for each group of questions, if these abilities have increased from time 0 (when the project started) to time 1 (after 1 year), it makes sense to calculate the median or the mean or the total for each observation within each group of questions at time 0 and time 1 and then use the sign test to compare these 2 new variables?
Thanks a lot.

[Fei Wang]

Yes, I think it's reasonable to do so. Or you may test distributional difference of each question between time 0 and 1. For example, you may find that for the 6 questions within a group, 4 of them change distributions and 2 do not, which could enrich your research findings.

[Daniela Rozzi]

Ok, thank you for your help