STAT1008 Lecture Notes - Lecture 17: Effect Size, Sample Size Determination, Multiple Sclerosis
STAT1008 Week 5 Lecture C
● Significance Level:
○ If the p-value is less than alpha, the results are statistically significant, and we
reject the null hypothesis in favor of the alternative
○ If the p value is not less than alpha, the results are not statistically significant,
and our test is inconclusive
○ Often alpha = 0.05 by default, unless otherwise specified
● Hypothesis Test:
○ E.g. Red Wine and Weight Loss
■ Resveratrol, an ingredient in red wine and grapes, has shown to promote
weight loss in rodents and has recently been investigated in primates
(specifically, the grey mouse lemur)
■ In the test to see if mean resting metabolic rate is higher after treatment,
the p-value is 0.013
■ Using alpha = 0.05
● Is this difference statistically significant? Yes because p value is
less than alpha thus results are statistically significant and we
reject Ho. There is evidence that mean resting metabolic rate is
higher after receiving resveratrol
● Give a formal generic conclusion about Ho
● Give a conclusion in context
■ In the test to see if the mean resting body mass is lower than treatment,
the p-value is 0.007.
■ Using alpha = 0l05
● Is this difference statistically significant? The p-value is lower than
alpha = 0.05, so the results are statistically significant and we
reject H0. There is evidence that mean body mass is lower after
receiving resveratrol.
● Ho: mub = mut and mut < mub
● Give a formal generic conclusion about H0
● Give a conclusion in context
■ In the test to see if locomotor activity changes after treatment, the p-value
is 0.980
■ Using alpha = 0.05
● Is this difference statistically significant? The p-value is not lower
than alpha, so the results are not statistically significant and we
don’t reject H0. The data does not provide sufficient evidence to
conclude that locomotor activity changes after treatment
● Give a formal generic conclusion about H0
● Give a conclusion in context
■ In the test to see if the mean food intake changes after treatment, the p
value is 0.035.
■ Using alpha = 0.05
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Document Summary
If the p-value is less than alpha, the results are statistically significant, and we reject the null hypothesis in favor of the alternative. If the p value is not less than alpha, the results are not statistically significant, and our test is inconclusive. Often alpha = 0. 05 by default, unless otherwise specified. Resveratrol, an ingredient in red wine and grapes, has shown to promote weight loss in rodents and has recently been investigated in primates (specifically, the grey mouse lemur) In the test to see if mean resting metabolic rate is higher after treatment, the p-value is 0. 013. Yes because p value is less than alpha thus results are statistically significant and we reject ho. There is evidence that mean resting metabolic rate is higher after receiving resveratrol. In the test to see if the mean resting body mass is lower than treatment, the p-value is 0. 007.
