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Hypothesis Testing

Hypothesis Testing. Part IV – Practical Significance. This video is designed to accompany pages 95-116 in Making Sense of Uncertainty Activities for Teaching Statistical Reasoning Van- Griner Publishing Company. Multivitamins and Cancer. Multivitamins and Cancer.

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Hypothesis Testing

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  1. Hypothesis Testing Part IV – Practical Significance

  2. This video is designed to accompany pages 95-116 in Making Sense of Uncertainty Activities for Teaching Statistical Reasoning Van-Griner Publishing Company

  3. Multivitamins and Cancer

  4. Multivitamins and Cancer • Actual difference was 8% fewer cancers in treatment group. • You can think of this as the actual “effect size” • The fact that this difference was statistically significant means that it was big enough that the alternative could be accepted with a Type I error rate (false positive rate) that was low enough (probably 0.05) to be tolerable. • This does not mean that the difference is big enough to care about clinically. When it comes to cancer reduction, though, 8% might catch our attention. • Still, this question is not answered in the article, and the author does call the effect “small.”

  5. Mental Illness and Obesity

  6. Mental Illness and Obesity • Many fitness programs achieved “statistically significant” weight loss results. • That means that while in the program the weights of participants dropped enough to make it safe to infer that there would be weight loss in the larger population. • But the authors also note that in most of these programs the weight loss was not “clinically significant.” • They say elsewhere in the article that in this context clinically significant means more than 5% of one’s body weight.

  7. Apnea in Your Stockings

  8. Apnea in Your Stockings • Statistically significant reduction. • Effect size seems to be about a 36% reduction in apnea episodes. • Average number of episodes decreased from 48 per hour to 31 per hour. • But the blog author is concerned because this still leaves the “average” severe patient in the severe category.

  9. Coffee and Pregnancy

  10. Coffee and Pregnancy • Women who had less than 200 mg of coffee a day experienced a 40% increase in miscarriage risk compared to women who had no caffeine during pregnancy. • Dr. Aaron Caughey, a perinatologist at UCSF, is quoted in the article as saying “I would probably not even recommend a cup a day, based on this.” • Statistically “safe” is not ultimately always reassuring. • There is solid evidence to suggest that a lot of practically meaningful findings may be getting suppressed because they are not statistically significant.

  11. One-Sentence Reflection Statistical significance is a mathematical way of assessing whether treatment differences are big enough to be considered unlikely to have happened by chance; whereas practical significance addresses whether the observed difference is big enough that it is practically worth caring about.

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