HUMBEHV 3HB3 Lecture Notes - Lecture 15: Central Limit Theorem, Null Hypothesis, Statistical Hypothesis Testing
11 Sep 2018
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P of cancer given positive is 15 over 15 plus 300, p of positive is 15 plus 300 over 10 thousand. In example we considered the probability of observing group differences that were greater than and less than the mean: however our original hypothesis was directional. Increased power leads to over estimation of height: group a mean should be greater than group b mean, we need to make directional null hypothesis testing to ensure this directionality is correct. General strategy: compare this persons data to what the null hypothesis says, we pick critical values of z such that if the observed z value falls in the rage we will not reject the null hypothesis. If it falls beyond or outside of the critical points we will reject the null hypothesis: we can use the sample standard deviation as an unbiased estimate of the population variance. It is unimodal, it is symmetrical around zero: degrees of freedom alter kurtosis.
