Help for simple regression

#1
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)

This statement clearly tell 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
 
#3
No I don't.
If fact, my complete research question is:
"Can we say that the number of hours of Internet use increases with Internet purchase? This influence of Internet purchase on the number of use can it be explained by an attitude becoming more favorable as we know Internet? "
with the variables:
- Use of Internet per week (Use in hours)
- Internet attitude (Attitude_Internet 1 = very unfavorable, 7 = very favorable)
- If respondent has already made a purchase on the Internet (1 = yes, 2 = no)

For the second part of the research question I made a mediation and I change my variable purchase in no = 0 and yes = 1 because when it was 1=yes 2=no that was confusing me. My résuflats are:
I did a mediation with process in SPSS
(Variable z = mediator = Attitude_Internet
Variable x = independent variable = Purchase_Internet
Variable y = dependent variable = Use_Internet)
The results are:
a path= 1,38 (significant)
b path = 1,6517 (significant)
c path= 3,357 (significant)
c' path = 1,087 (p>0,05 -> non significant)