A researcher measured the relationship between political affiliation (Republican, Democrat) and attitudes toward gun control. She had participants state their attitude toward gun control using a 7-point rating scale from 1 (completely against) to 7 (completely support). The following table lists the results of this hypothetical study.
Political Affiliation ________________________ Attitudes Toward Gun Control
_______X____________________________________________Y_____________
Democrat .............................................................1
Democrat .............................................................3
Democrat .............................................................1
Democrat .............................................................1
Democrat .............................................................3
Republican ...........................................................7
Republican ...........................................................6
Republican ...........................................................5
Republican ...........................................................6
Republican ...........................................................4
Republican ...........................................................6
Republican ...........................................................5
(a) Compute the point-biserial correlation coefficient.
(b) Using a two-tailed test at a .05 level of significance, state the decision to retain or reject the null hypothesis. Hint: You must first convert r to a t statistic.