An educational psychologist has developed a new 20-item test to assess risk taking among college students. In an effort to establish the validity of his new test, he has the 25 students in his first-year seminar take both his test and an already validated 50-item measure of risk taking. He correlates the students' scores on the two measures and finds they are correlated (+.78).

1. What correlation statistic should the psychologist have computed?
2. What is the critical value of the correlation (found in the table of critical values)?
3. Can the psychologist conclude that his new test is valid? Explain your answer.
4. If both tests are assessing risk taking, why didn't he get a perfect correlation?

A professor is interested in whether attendance on the first day of class is related to final grades. She collects information from an introductory and an advanced class for a total of 62 students and finds that first-day attendance (yes/no) is related to final course grades (+.26).

1. What correlation statistic should the psychologist have computed?
2. What is the critical value of the correlation (vs. the obtained value)?
3. What can the psychologist conclude about first-day class attendance and grades?