Lecture+9+su10+_hypothesis+testing-part+2_

Lecture+9+su10+_hypothesis+testing-part+2_ - Sociology 210...

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02/23/11 Soc 210 summer 2010 1 Sociology 210 Lecture 9: Hypothesis Testing, Part 2
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02/23/11 Soc 210 summer 2010 2 Steps in Hypothesis Testing 1. State the Hypotheses One-tailed test vs. two-tailed test Null hypothesis, Alternative Hypothesis 2. Set the Criteria for a Decision alpha, critical value (z*), critical region 3. Collect Data and Compute the Test Statistic calculate standard error 4. Make a Decision
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02/23/11 Soc 210 summer 2010 3 Once you collect your data and calculate the sample mean, then you calculate the “ test statistic: the z -score of the observed sample mean relative to the hypothetical sampling distribution (i.e., the sampling distribution you would get if H 0 were correct about the population mean) The test statistic shows how far away your observed sample mean is from the mean of the the hypothetical sampling distribution (the distribution of sample means under the null) Make sure you use the standard error (not the standard deviation) in the denominator chance to due difference difference obtained and between error standard mean population ed hypothesiz - mean sample 0 = = - = μ σ X X Z X 3. Collect Data & Compute Test Statistic
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02/23/11 Soc 210 summer 2010 4 There are two comparisons you can make to decide whether to reject or fail to reject the null hypothesis (they give you the same answer) A. You can compare the value of the test statistic, z , to the critical value z* If the test statistic falls in the critical region of the hypothetical sampling distribution, it means that such a value would be very unlikely if μ 0 were true, so you reject H 0 You reject H 0 if | z | | z *| 4. Make a Decision: Reject or Fail to Reject H 0
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02/23/11 Soc 210 summer 2010 5 4. Make a Decision: Reject or Fail to Reject H 0 B. You can compare the P -value to α The P -value is the probability of obtaining a value of the test statistic if the null hypothesis were true (i.e., how unlikely is it that you would have obtained this value of the test statistic if H 0 were true) α is a value the researcher sets for how small the P -value has to be before we reject H 0 You reject H 0 if p < α
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02/23/11 Soc 210 summer 2010 6 Comparing p and α It is more common in practice to compare the P -value (associated with z ) to α – The P -value is the probability that H 0 is true, for a given value of the test statistic, z In other words, p is the probability of drawing a sample (from
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Lecture+9+su10+_hypothesis+testing-part+2_ - Sociology 210...

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