Chi square goodness of fit Is your die
- Slides: 7
Chi- square goodness of fit
Is your die fair— 1 more time. Roll your die 120 times. Write down the number of each roll. Example: Observed 25 20 35 20 19 20 14 20 Expected 16 20 11 20
Dice ---Requirements § What are the requirements for the Chisquare test? EASI § E—eighty percent of the expected cells are greater than 5. (not observed cells— expected cells!) § S—representative sample. § I—Independence.
Run test!! § Note—Chi-square test is not normal. § Must figure out the chi-square sum and degrees of freedom. § Chi-square sum: (O-E)^2/E and then add them all up. Look up on formula sheets. § On calculator X^2 cdf(x^2, 10^99, df)---also use formula sheets. § Sum is 1. 25 + 11. 25 +. 05 + 1. 8 + 4. 05 § = 19. 2
Run test!! § X^2 cdf(19. 2, 10^99, 5) =. 0018 Reject Ho @ alpha. 01. There is evidence to suggest my die is not balanced.
What about Ho and Ha? § There are no symbols for the chi-square. However, it is always one-sided, even though the word “different” is used. § Ho: The dice will roll as you would expect. (there is an implied = here) § Ha: the die is different than you would expect.
Demographics. § La Quinta is approximately 79% Asian, 15% Hispanic, 5% white and 1% other. § Does Mr. Snider’s stats classes reflect this diversity? Run the appropriate test, verify your requirements, and write a conclusion.
