You asked, "How can I check if I don't have to reverse my IV and my DV?"
To answer that, you need to think about the timing of events and
measurements. For example, in one common study design in epidemiology (the
cohort study), one starts with a group of people (a cohort) who are all free
of the outcome of interest (e.g., an internet purchase) but whose exposure
status (hours/week of internet in your example) is known. Subjects are then
followed forward over time, and (new) occurrences of the outcome are
recorded. If this was your study design, it would be clear that Purchase is
dependent and hours/week explanatory.
But this is not your study design. It sounds to me like you have historical
information for both variables. This makes it more like a cross-sectional
design (sometimes called snapshot study), where both variables are measured
at the same time. In that case, how you assign variables to explanatory and
dependent roles is less clear, and usually driven by the wording of the
research question.
The wording you used in stating the research question ("Can we say that the
number of hours of Internet use increases with Internet purchase?") seems to
me consistent with treating hours/week as dependent on purchase. Is that
the wording that was given to you in the homework assignment? Or have you
paraphrased it?
HTH.
p.s. - The simple linear regression you proposed is equivalent to the
unequal variances version of the independent groups t-test. See Jerry
Dallal's note, for example:
http://www.jerrydallal.com/lhsp/treg.htm
chamarique wrote
> my research question is: "Can we say that the number of hours of Internet
> use increases with Internet purchase?" with the variables: - Use of
> Internet per week (Use in hours) - If respondent has already made a
> purchase on the Internet (1 = yes, 2 = no)
>
> Therefore, this statement told me that my dependant variable is number of
> hours of Internet use and my independant variable is Online purchase. But
> that seems me a little weird. How can I check if I don't have to reverse
> my IV and my DV ? (I use SPSS) Thank you
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Bruce Weaver
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