PSYC1040 Lecture Notes - Lecture 11: William Sealy Gosset, Null Hypothesis, Square Root
Document Summary
Testing hypotheses about a sample mean: z = m-u/pop sd, good to use when testing differences between means when population sd is known, use t-test when population sd is not known, t = m-u/sm. Guinness beer is responsible: william sealy gosset (1876-1937, guinness brewery in dublin, statistician for brewery, developed t-test and t distribution. "student" was the name he used, forced to use that. Difference between t and z: t-test = estimate of population sd based on sample sd to produce estimate of standard error of mean, degrees of freedom = t-test, t-test = t distribution, z-test = normal distribution. Determining standard error: when you know population sd = z-test, when you don"t know population sd = t-test, s2m = s2/n, sm = square root of s2m, sm = s/square root of n. Don"t know sd: distribution of means isnt necessarily normal curve, df - degrees of freedom = n-1.
