Answer:
Standard Deviation (cont’d)Weights(pounds):110 120 130 140 150 150 160 170 180 190Deviation scores(x) forM = 150:-40 -30 -20 -10 0 0 10 20 30 40 Squared deviation scores(x2):1600 900 400 100 0 0 100 400 900 1600Sum of squared deviation scores:1600+900+400+100+0+0+100+400+900+1600 = 6000SD= √(6000/(N-1) = SD= √(6000/(9) = 25.82Standard Deviation Interpretation•Provides a “standard”—the SDindicates the average amount of deviation of scoresfrom the mean•Tells you how wrong, on average, the mean is•An SDprovides valuable information when the distribution is normal:–There are approximately three SDsabove and below the meanin a normal distribution•In a normal distribution, a fixed percentage of cases lie within certain distances from themeanSDs and Individual Scores•A person who scores one SDbelow the mean has a higher score than 16% of the cases (2.3% + 13.6%)•A person who scores one SDabove the mean has a higher score than 84% of the cases (50.0% + 34.1%)Example: Midterm marks: