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Stock Market Gyrations Following is a sample of the day-by-day change, rounded to the nearest 100 points, in the Dow Jones Industrial Average during 10 successive business days around the start of the financial crisis in October 2008:42
–400, –500, –200, –700, –100, 900, –100, –700, 400, –100
a. Compute the mean and standard deviation of the given sample. (Round your answers to the nearest whole number.)
b. Assuming that the distribution of day-by-day changes of the Dow during financial crises is symmetric and bell shaped, then the Dow falls by more than ___ points 16% of the time. What is the percentage of times in the sample that the Dow actually fell by more than that amount? [hinT: See Example 2(b).]
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