STAT 210 1st EditionLecture 8Outline of Last Lecture I. Descriptive StatisticsII. DistributionsOutline of Current LectureIII. Measures of CenterIV. Distributions Current LectureV. Goal: numerically describe the centerVI. Describe value of a known population parametera. Central locationb. Dispersion parameter – measure spread or variabilityVII. Population:a. = meanb. = standard deviationc. = proportionVIII. Samplea. X bar = sample meanb. S = standard deviationc. P hat = proportionIX. n = # of observations in sampleX. N = populationXI. x1 = value of first observationXII. x2 = value of second observationXIII. Measure of central locationa. Mean = averageb. Population mean = Mc. Usually a parameterXIV. Population mean is estimated by sample meana. X bar = (∑x/ n) = (x1+x2+x3)/nXV. Median (more resistant to outliers)a. = pop. Medianb. M = sample mediani. Order data from smallest to largestii. Calculate median location (n+1)/2iii. Calculate medianiv. If n is odd then (n+1)/2 and you’ll get a whole numberv. If n is even then (n+1)/2 will be a fractionvi. Add/subtract the numbers and it’ll give ou the 11th and 12th observationsXVI. Distributionsa. Mean is point where a histogram balancesb. For symmetric distributions mean and median will be nearly the
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