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Chi Square and Corn

Chi Square and Corn. What does Chi-square analysis tell us ?. If the difference between your observed results and expected results are due to random chance or not.

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Chi Square and Corn

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  1. Chi Square and Corn

  2. What does Chi-square analysis tell us? If the difference between your observed results and expected results are due to random chance or not. EX –flip a coin enough and you would expect to get heads 50% of time and tails 50% of time. If this number is way off even after 1,00 tosses then something else besides randomness is occurring

  3. How’s it works Calculation to use is X2 = ∑ (observed – expected)2 expected Table to set up

  4. How it works continued • Determine degrees of freedom – it’s one less than the number of possible outcomes Ex – expect 4 different phenotypes, degrees of freedom is 3

  5. What are you looking for? • p = .05 is the cut off for accepting or rejecting you hypothesis that the difference is due to random events • p more than .05 means that your hypothesis may be supported • p less than .05 means hypothesis not supported

  6. What? • p is probability of an event occurring due to randomness If p = .50 then the difference between observed and expected results is due to random events 50% of time

  7. How it works • Once you have your degrees of freedom and Chi square sum, go to the distribution table

  8. You explain • If p = .05 then what does that mean? the difference between observed and expected results is due to random events only 5% of time so – something else must be going on! Your hypothesis can’t be supported b/c something else besides random events is playing a role in the outcome

  9. What are you looking for? • p = .05 is the cut off for accepting or rejecting you hypothesis that the difference is due to random events • p more than .05 means that your hypothesis may be supported • p less than .05 means hypothesis not supported

  10. Try it • P = Purple • p = Yellow • S = Smooth PpSs x PpSs • s = Shrunken What are the expected results? Hypothesis? 9:3:3:1 due to independent assort of alleles

  11. Results analysis • Observed results: An ear of corn has a total of 381 grains, including 216 Purple & Smooth, 79 Purple & Shrunken, 65 Yellow & Smooth, and 21 Yellow & Shrunken. • Expected?

  12. Table, Chi Square and Degrees of Freedom Df: SUM of Chi Squares:

  13. Hypothesis supported?

  14. Try this one • Same hypothesis: independent assort therefore 9:3:3:1 outcome • Observed: An ear of corn has a total of 389 grains, including 219 Purple & Smooth, 70 Yellow & Smooth, and 100 white.

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