Stat2013

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Course work IICB, 2013; Biostatistics

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Stat2013

  1. 1. Chi square test Sucheta Tripathy, Biostatistics course work IICB,Nov, 2013
  2. 2. Definitions •Model or Hypothesis •Null Hypothesis •There is no significant difference between the 2. TRUE FALSE •Goodness of fit
  3. 3. What you need • A probability value • Degree of freedom • A contingent table Determine if the deviation is due to chance Accept 10% Reject
  4. 4. Chi Square Test
  5. 5. Example 1 • Mendellian law of dominance A -> Tall (Dominant) a -> Dwarf (recessive) Aa is ……. Aa X Aa A a X A a 639 Tall and 281 dwarf AA Aa Aa aa Chi square requires that you have numeric values Chi square should not be calculated if the expected value is less than 5
  6. 6. Example 9:3:3:1
  7. 7. Example Number of sixes 0 1 2 3 Number of Rolls 48 35 15 03 p1 = P(roll 0 sixes) = P(X=0) = 0.58 p2 = P(roll 1 six) = P(X=1) = 0.345 p3 = P(roll 2 sixes) = P(X=2) = 0.07 p4 = P(roll 3 sixes) = P(X=3) = 0.005 P(k out of n) = n! k!(n-k)! http://www.mathsisfun.com/data/binomial-distribution.html pk(1-p)(n-k)

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