Chapter 18 part 2

Chapter 18 part 2 - Two Sample t Tests Example A random...

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Two Sample t Tests Example : A random sample of 25 students were given gum before an exam. Another random sample of 35 students were not given gum. The students with gum had an average score of 82 and a sample std. dev. of 15. The students without gum had an average score of 79 and a std. dev. of 18. Test to see if chewing gum increases the average exam score. 1 Chapter 18
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Two Sample t Tests Solution: 1) 2) 3) 4) 2 Chapter 18
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Chapter 18 3 Robustness of t Procedures The two-sample t procedures are more robust than the one-sample t methods, particularly when the distributions are not symmetric. When the two populations have similar distribution shapes, the probability values from the t table are quite accurate, even when the sample sizes are as small as n 1 = n 2 = 5. When the two populations have different distribution shapes, larger samples are needed. In planning a two-sample study, it is best to choose equal sample sizes. In this case, the probability values are most accurate.
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Chapter 18 part 2 - Two Sample t Tests Example A random...

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