Actuarial Science 2427A/B Lecture Notes - Lecture 4: Messier 81, Variance, Standard Deviation
9 Jan 2015
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If sigma is not given, cant do a z test. Therefore, always check if sigma is given or not: degrees of freedom (df) = n - 1. As the df increase, the better the sample represents. Therefore, if df is infinite, then it will represent the actual population (since sample will equal population: when df is small, shape of graph is flat and spread out. Example1: a random sample of participants in a new exlaxation study n=25, were evaulated on anxiety levels. The sample has m = 81, with s = 10, compare to u = 85, use alpha= 0. 05. T = m - u / 2 -> 85 - 81 /2 = -2. There is no significant difference in anxiety scores when the new relaxation technique is used, t(24) = - 2. 00, p>0. 05 (fail to reject h0), m=81, sd=10.
