A psychologist wonders whether performance by students in her class has fallen this semester. Among students in past semesters, mean GPA 3.1 and GPA .30. She decides to adopt. 05 and power .8. If the difference between present students and those in past semesters is as great as .09 grade point, she would want to know it.
(a) State the null hypothesis and alternative hypothesis for a two-tailed test.
(b) What should the size of the sample be to test this null hypothesis? Use the power curve chart.