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**Unformatted text preview: **l hypothesis) and what we OBSERVED. How big is this difference? We will measure it using a new statistic called the chi- squared statistic. To calculate the chi- square statistic: 1. Find (O – E) for each of the four cells. That is, (observed value – expected value). 2. Square the values from step 1. You should notice that they are all the same. 3. Divide each of the values from step 2 by the expected values in each cell. 4. Add the values in step 3. The result is referred to as chi- squared. 2
(observed − expected) 2
Χ=∑
expected
all cells In our example, we have: 2
2
2
2
(50 − 42) + (100 − 108) + (34 − 42) + (116 − 108) = 4.2 chi- squared=
42
108
42
108 € We use this number to test our hypothesis as follows: 1. State the null hypothesis: There is no relationship between chewing Nicorette and getting a sore throat. Specifically, you are no more or less likely to get a sore throat after chewing Nicorette than after chewing a placebo gum. 2. Set up the study as described above and derive the EXPECTED and OBSERVED values for the four cells....

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