Independent & Dependent Variables
In our example where we hypothesized bullying as potentially causing depression:
Bullying would be viewed as the independent variable (presumed causal variable / the x-variable).
Depression would be viewed as the dependent variable (presumed effect variable / the y-variable).
Cause --> Effect
When x increases --> y increases.
As we’ve mentioned, we can’t really tell directionality or causation in a cross-sectional study. Nonetheless, we are free to make presumptions as long as we clearly state this in our research reports.
It is a bit easier to tell directionality in a longitudinal study.
Bullying would be viewed as the independent variable (presumed causal variable / the x-variable).
Depression would be viewed as the dependent variable (presumed effect variable / the y-variable).
Cause --> Effect
When x increases --> y increases.
As we’ve mentioned, we can’t really tell directionality or causation in a cross-sectional study. Nonetheless, we are free to make presumptions as long as we clearly state this in our research reports.
It is a bit easier to tell directionality in a longitudinal study.
Testing Understanding
Click on the link below and it will take you to a study in South Africa. (Yup, click on the words in blue).
A prospective longitudinal model of substance use onset among South African adolescents
The researchers claim that teens that was the most likely to try all substances by the beginning of ninth grade comprised of those who began substance use by smoking cigarettes. Thus, Cigarettes is a Gateway Drug.
Q: How did they come to this conclusion? Did they use a cross-sectional or longitudinal study?
Q: Did they measure the same participants across time, or different participants?
Q: How many times were these measurements done?
Q: Would you have done anything differently if you were measuring substance use in teens? What would that be?
A prospective longitudinal model of substance use onset among South African adolescents
The researchers claim that teens that was the most likely to try all substances by the beginning of ninth grade comprised of those who began substance use by smoking cigarettes. Thus, Cigarettes is a Gateway Drug.
Q: How did they come to this conclusion? Did they use a cross-sectional or longitudinal study?
Q: Did they measure the same participants across time, or different participants?
Q: How many times were these measurements done?
Q: Would you have done anything differently if you were measuring substance use in teens? What would that be?