Likert Data Analysis in Excel

Hi,

I'm new to the forum - though I have browsed and found the resources helpful for a long time. Thank you to all who contribute here.

I have an issue with some data that I can't see covered elsewhere. I have conducted a study on whether 3 different groups of students found our mobile website useful towards learning. The survey covers a range of areas, from content of the site, to whether mobile learning has improved their ability to study.

In total I have 16 Likert type questions - all with a scale of Strongly Disagree, Disagree, Neutral, Agree and Strongly Agree.

Immediately, I can observe from the whole sample (all 3 groups - n=601) that the results will be skewed to the right (Agree/Strongly Agree) for nearly all 16 Likert questions.

I'm unsure what type of tests I can use to illustrate whether there was a significant difference between the 3 groups of participants (biology/geography/maths students). Kruskal-Wallis seems like an option, but I don't know how to apply this to Likert type data using Excel.

Of the 601 sample, the group sizes are not equal. 281 are biology students, 267 are geography students and 53 are maths students. Does this affect what test I can use?

I have already created charts for each question, comparing the 3 groups % response to the question.

However, I'd like to take this further, and not quite sure how. I'd like to treat my data as ordinal rather than assuming it is interval.

From the extensive reading I have done, this would have been easier with only 2 groups of students, but I have what I have.

Any ideas would be greatly appreciated!