The paper "A Cross-National Relationship Between Sugar Consumption and Major Depression?" (Depression and Anxiety [2002]: 118-120) concluded that there was a correlation between refined sugar consumption (calories per person per day) and annual rate of major depression (cases per 100 people) based on data from six countries. The following data were read from a graph that appeared in the paper:
a. Compute and interpret the correlation coefficient for this data set.
b. Is it reasonable to conclude that increasing sugar consumption leads to higher rates of depression? Explain.
c. Do you have any concerns about this study that would make you hesitant to generalize these conclusions to other countries?