Predicting brain density from number of Facebook friends (cont.) Recall that we previously explored the potential positive relationship between the number of Facebook friends someone has and their brain density based on data from 40 volunteer university students. The null hypothesis is that there is no association between brain density and number of Facebook friends in the population. We rejected this null hypothesis before because the observed slope (and correlation coefficient) were too far in the tail of the (respective) null distribution to be attributed to random chance. We will further explore this analysis in this exploration using a theory-based approach. Theory-based approach When using the theory-based approach for regression you can write your hypotheses in terms of population parameters. The relevant population parameters are the population slope (indicated by the Greek letter ) and the population correlation (indicated by the Greek letter ). PARTICIPATION ACTIVITY 4.10.1: Question 1. What is the equivalent statement of the null hypothesis in terms of the population slope