Likert scale analysis - grouped items

#1
Good morning,

I am currently analyzing a Likert scale questionnaire (5 points) of 28 items.
The items of the questionnaire are grouped into several categories, e.g. the first three items are grouped into a category called "challenge", corresponding to a topic to discuss in the study. In contrast, the two following items pertain to another category, named "feedback".

I started my analysis by calculating the scores for each category (e.g. respondent 1: score for Item 1 = 3, score for Item 2 = 4, score for Item 3 = 3, total score for the category = 10), and then the mean of all respondents. However, the theoretical minimal and maximal values vary according to the categories, as each category contains a different number of items. For example, I obtain a mean of 10.85 for the "challenge" category, for a theoretical maximum of 15. In contrast, I obtain a mean of 9.15 for the "feedback" category, for a theoretical maximum of 10.
These differences in the number of items make the comparison between categories difficult. So my question is: how can I analyse and compare the means of the different categories on the same basis? I guess there is a calculation I should do. Furthermore, should I also "homogenize" results for comparing standard deviations, variances, median and modes among categories?

Second, I would like to illustrate the results (mean, standard deviation, variance, median and mode) for each category with a graphical chart (one chart per category), so to guide the reader. Which type of chart would you recommend?

I hope I am clear enough, please let me know if I should further detail my questions.
Thanks a lot in advance, and best regards :)
Frédérique
 
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