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Chapter 3 Descriptive Statistics

3.2 Measures of Variability

Range

Interquartile Range

Population Variance

Sample Variance

Standard Deviation

Coefficient of Variation

Home Work

1. Consider the data the sample size 5 with data values of 10, 20,12,17,16. Compute the range and interquartile range.
2. Consider the data the sample size 5 with data values of 10, 20,12,17,16. Compute the variance and standard deviation.
3. Consider the data the sample size 8 with data values of 27, 25, 20, 15, 30, 34, 28, and 25. Compute the range, interquartile range, variance, and standard deviation.

Application Home Work (DO IT ON EXCEL)

1. Police records show the numbers in the file Crime.xls of daily crime reports for a sample of days during the winter months and a sample of days during the summer months.

a. Compute the range and interquartile range for each period

b. Compute the variance and standard deviation for the each period.

c. Compute the coefficient of variation for each period.

d. Compute the variability of the two period.

2. The American Association of Individual Investors conducts an annual survey of discount brokers (AAII Journal, January 1997). Shown in Discount.xls are the commissions changed by a sample of 20 discount brokers for two types of trades: 500 shares at $50 per share and 1000 shares at $5 per share.
1. Compute the range and interquartile range for each type of trade
2. Compute the variance and standard deviation for each type of trade.
3. Compute the coefficient of variation for each type of trade.
4. Compute the variability of cost for the two type of trade.