Chi squared test Today working towards Outline what
- Slides: 8
Chi – squared test
Today working towards…… • Outline what chi-squared is. • Identify when to use chi-squared • Demonstrate the application of chi-squared.
What is it? Pony weight Horse weight • Another wonderful stats test for 387 602 you to learn!! Area A B C D E 405 550 • Used to 420 find out a difference 700 No. of ponies 23 7 674 25 19 21 350 samples between seen 329 602 • Unlike a 500 t-test for each group 580 or category 425 there is only one data 720 point Total ponies 95
When to use it • When you have category data • When you have counted things into categories • When you have 2 or more categories
What to consider ………. • Each data point needs to behave independently. • Normal distribution does not matter • Do not use the % • No more than 20% of “expected” values should be less than 5
How to use it? Area A B C D E Total ponies No. of ponies seen 23 7 25 19 21 95 Null hypothesis – Ponies have no preference for areas of the forest.
Practice 1. What would the null hypothesis be? Breed Count of vomiting cases Collie 29 Jack Russel 38 Pug 32 Labrador 41 Westy 21 Staffy 12 Retriever 28 2. What is the expected value? 3. Complete the test 4. Write out the results.
Another practice of Chi squared. • A researcher has completed a study to outline the success of vet practices • Success is determined based on the number of awards obtained in the last 10 years • Develop a suitable hypothesis for the outlined research • Complete the correct stats test for the data set provided. Vet practice Number awards A 29 B 40 C 51 D 10 E 55
