Thread: What test to use?

Hi,

I am required to perform some statistical analysis on some data. I am measuring user opinion (given by a 4-point Likert Scale) on two different systems.

I have assigned numbers to the scale, such that 1=strong disagree, 4=strongly agree.

Is it satisfactory to simply compare the two tables - ie the modal value of system 1 is x, the modal value of system 2 is y - therefore one is better than the other?

Or, does some kind of statistical test need to be performed in order to even out errors associated with the average?

Sorry if I haven't explained this well enough, I'll be happy to clarify if necessary.

Originally Posted by samhogy

Hi,

I am required to perform some statistical analysis on some data. I am measuring user opinion (given by a 4-point Likert Scale) on two different systems.

I have assigned numbers to the scale, such that 1=strong disagree, 4=strongly agree.

Is it satisfactory to simply compare the two tables - ie the modal value of system 1 is x, the modal value of system 2 is y - therefore one is better than the other?

Or, does some kind of statistical test need to be performed in order to even out errors associated with the average?

Sorry if I haven't explained this well enough, I'll be happy to clarify if necessary.

Since you are handling categorical data, you may want to set up a contingency table. Then just run a chi-squared test at some fixed alpha value (level of your test). That may quantify things.

Check out this links:

Contingency table - Wikipedia, the free encyclopedia

Here is the statistic used,

[Pearson's chi-square test - Wikipedia, the free encyclopedia

Hi, thanks for your reply.

I'm not sure if this is the best solution to use. Likert scales give ordinal data, wouldn't reducing this to nominal data cause a 'loss' of information?

I was originally taking the mean from both Likert scales, and then calculating standard deviation. I'm not doing that anymore, as I don't think it's very accurate to treat Likert scale results as intervals.

Instead, I'm using the mode as a rough guide to the overall result for each Likert scale, and I'm using pie charts to compare the actual results.

Is this a more satisfactory method?

I think, in order to provide contextual information, I should give a sample question from my questionnaire:

"It is easy to create a game"
a) by hand:
Strongly disagree [] [] [] [] Strongly agree

b) using system:
Strongly disagree [] [] [] [] Strongly agree

You may have seen this, but this diagram may help you decide. I am not entirely sure how to approach this, but none of tests recommended in the diagram are that difficult.

Choosing the Correct Statistical Test

Thanks very much. I was reading Human Computer Interaction by Dix Et. Al, which suggested the Mann-Whitney method. Your diagram just confirmed my choice.

Thanks very much for your input