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 observed results expected results expected results The calculated X 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 Step 2 determine your expected values Step 3 complete the Chi square chart Observed O 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 Expected E O E O E O E E Step 4 calculate your degrees of freedom P 0 05 0 01 Step 5 interpret results 1 2 3 84 5 99 6 64 9 32 CHI SQUARE TABLE Degrees of Freedom 5 6 7 3 7 82 9 49 11 07 12 59 14 07 15 51 11 34 13 28 15 09 16 81 18 48 20 09 Total