Question

Rejecting the null hypothesis that the population slope is equal to zero or no relationship and concluding that the relationship between x and y is significant does not enable one to conclude that a cause-and-effect relationship is present between x and y. Explain why?

Answer 1

Cause and effect relationship cannot be inferred from the significant slope of regression equation itself because regression is about correlation relationship between the variables whereas the cause and effect relationship is known by studying several other parameters of context, qualitative measures, confounding variables, etc,. Cause and effect relationship is beyond quantitative data. Regression equation is obtained using quantitative data and is confined to such data.

So, if the null hypothesis is rejected, then the correlation relationship between the variables is significant but there is nothing to say about cause and effect relationship.

Moreover, any unrelated variables can have a significant correlation and it does not mean change in one variable is causing the change in the other variable. The context and looking for the confounding effect is important here.

Cause and effect relationship is beyond the data. The quantitative data is one of the parameters to find cause and effect relationship between the variables, but not the entire thing.