Final answer:
The statement that RR = 1 means the treatment has no effect on the outcome is true. A positive correlation does not necessarily indicate health benefits; it only shows a direct relationship. If the correlation coefficient (r) is 0, it indicates no linear relationship and cannot be used for predictions.
Step-by-step explanation:
The statement "RR = 1 means that the treatment does not affect the outcome" is true. RR stands for Relative Risk, and it is a measure used in epidemiology to determine if there is an association between exposure to a particular treatment and the occurrence of an outcome. When RR equals 1, it indicates that the incidence of the outcome is the same in both the treatment and control groups, hence the treatment has no effect. Conversely, an RR less than 1 suggests a protective effect of the treatment, while an RR greater than 1 suggests an increased risk of the outcome due to the treatment. The fact that all subjects experienced both treatments and that the order of treatments was randomly assigned helps to eliminate the influence of confounding variables, thus strengthening the validity of the study.
Regarding the question about a positive correlation indicating health benefits, this statement is false. A positive correlation only means that there is a direct relationship between two variables, but it does not necessarily imply health benefits. For instance, there could be a positive correlation between smoking and lung cancer, but this certainly does not imply that smoking is beneficial to health.
Lastly, the idea that "It doesn't matter what the degrees of freedom are because r = 0 will always be between the two critical values, so r is not significant and may not be used for predictions" speaks to the concept of statistical significance in correlation studies. If the correlation coefficient (r) is 0, it suggests that there is no linear relationship between the variables, and thus, it cannot be used to make predictions, regardless of the degrees of freedom.