I am writing an essay based on a survey I made.

First I set my hypothesis = Who is an impulsive buyer tend to be loyal to shop X.

Than using "marketing scales book" I set different scales for each element:

  • Impulsive buying tendency: I tend to buy things without thinking, I buy on impulse.
  • Store loyalty: I love spending my time at store X, I am a loyal customer of store X, I feel in touch with store X.

Than I asked how they agreed 1-7 for each one.

Now I have to test my hypothesis… but witch is the best way?

Is there a method to test all 2 scales representing IMPULSIVENESS VS 3 scales representing LOYALTY one shot, as a group so it will be fully representative or I have to test every single scale of impulsiveness vs. single scale of loyalty and than, I made a mean?


1 Answer 1


Generally speaking, you would want to use the scale scores (e.g. the mean rating across all three impulsiveness items, etc.) in any subsequent analysis (correlation, test of differences, etc.)

The reason for that is that having several items increases the reliability (and therefore ensures a lower standard error of measurement, more precise estimation, higher statistical power, etc.). Intuitively, item-specific error variance “averages out” and the scale score provides a better measure of the underlying construct with a higher “resolution” than the original 1-7 format. This is the whole point of multi-item scales (and, in fact, of Rensis Likert's work as he focused on the combination of several items and not particularly on the item's response format commonly associated with his name).

Of course, this only works well if the items really do measure the same thing and satisfy some other assumptions. Traditional scale building techniques (factor analysis, etc.) are intended to document that and select “good” items to include in a scale. Since what you have is apparently an ad hoc scale with a limited number of items and probably a small number of observations, there is not much else you can do but assume the items really do form a reasonable scale based on your personal judgment of their meaning.

The worse thing that could happen is not so much a failure to find a meaningful effect (which is of course perfectly possible but presents less risk of being misinterpreted). Rather, it would be to find an effect that looks interesting but is in fact driven by one or two items and doesn't exactly means what you think it means based on your interpretation of the whole scale.

Alternatively you could still analyze each item separately (by computing correlations if I understood you correctly) but you will probably run into several problems: reduced power/attenuated correlations, potentially conflicting results, etc. If there are some meaningful differences between the items, this could be the only way to make sense of the results (imagine, say, that “spending time in store X” is mainly driven by interior design and “loyal customer” by pricing, what sense does it make to subsume them in a single measure?).

  • $\begingroup$ Thank you very much for your reply. I didn't mentioned that I am doing this with SPSS. So do you thing would be fare if I: Compute variable- creating a new variable containing the mean of the 3 scales and another containing the 2 scales. Than I do cross tabs with this two items so I can see if there is correlation between the two! Would it be fare to test my hypothesis? Thank you $\endgroup$
    – Stefano
    Jul 16, 2013 at 9:26
  • $\begingroup$ sorry I mean Contingency tabs $\endgroup$
    – Stefano
    Jul 16, 2013 at 9:32
  • $\begingroup$ @Stefano I don't see how contingency table would apply but computing two variables, one for each scale, is indeed what I suggested (with all the caveats I detailed in my answer). For the rest, you now seem to be asking a new and completely different question. The best thing to do is (1) use the search function to find previous questions on correlation and (2) if needed ask another question, providing more details on your study and your objectives. $\endgroup$
    – Gala
    Jul 16, 2013 at 9:44
  • $\begingroup$ Also, if my answer was useful, a positive vote/accepting the answer would be appreciated. $\endgroup$
    – Gala
    Jul 16, 2013 at 9:45
  • $\begingroup$ Hi, the question is the same, because I didn't get how to deal with it. You have been very helpfull theoretically but on practices how could test my hypotesis? $\endgroup$
    – Stefano
    Jul 16, 2013 at 9:57

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