Reminders: Chi-square is a form of statistical analysis used to compare the actual results (observed) with the expected results. The equation tests the null hypothesis for the problem being analyzed. The formula for Chi Square is: X-Elobserved results-expected results) expected results The calculated X2 value is always compared to the degrees of freedom chart as seen on the right. Unless instructed otherwise, compare your value to the p=0.05 row. CHI-SQUARE TABLE Degrees of Freedom P 1 2 3 5 6 7 0.05 3.84 5.99 7.82 9.49 11.07 12.59 14.07 15.51 0.01 6.64 9.32 11.34 13.28 15.09 16.81 18.48 20.09 1. A science teacher is bothered because of all the noise outside of his classroom each day. He decides to see where the noise is coming from and finds that several groups of freshman students use the water fountain located by the door to his classroom. There are three other water stations on campus, and after studying the frequency at which students visit each water fountain he becomes convinced that students prefer the water fountain by his room, rather than the other three fountains. The teacher assigns a student to be at each water fountain and count the total number of students getting water from each one. The data is as follows: water fountain #1 (by the teachers door): 45 students, water fountain #2: 36 students, water fountain #3: 25 students, and water fountain #4: 30 students. Is the teacher correct that students prefer to use the water fountain by his door? Step 1: state the null hypothesis: Step 2: determine your expected values Step 3: complete the Chi square chart: Observed Expected- E O-E (O-E) (O-E)2/E Step 4: calculate your degrees of freedom Step 5: interpret results Total