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Math Help - What test to use?

  1. #1
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    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.
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  2. #2
    Senior Member Danneedshelp's Avatar
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    Quote Originally Posted by samhogy View Post
    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
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  3. #3
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    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?
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  4. #4
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    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
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  5. #5
    Senior Member Danneedshelp's Avatar
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    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
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  6. #6
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    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
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