representative of the population

You are interested in knowing whether wealthier people are happier. You collected data from fifty people about their incomes and their overall happiness levels on a scale of 1 to 10. Upon analyzing the results, you find that the correlation coefficient has a value of −0.25. On the basis of this data, respond to the following:

How would you interpret the correlation coefficient in terms of strength and direction?

How would the results be affected if you increased the number of subjects in the study to one thousand? Why might that affect the overall correlation?

How important is it to randomly select subjects? Explain in detail using an example of a sample that might not be truly representative of the population.