86 CHAPTER 2 Descriptive Statistics Office rental rates 42 14 46 30 23 50 26 39 13 48 42 24 30 35 36 45 23 72 35 34 30 60 30 64 14 36 23 42 35 72 TRY IT YOURSELF 3 Refer to the study in Example 3. The recovery times (in days) for Group 2 are listed below. Find the sample variance and standard deviation of the recovery times. 53 25 41 36 19 22 42 34 Answer: Page A37 Using Technology to Find the Standard Deviation Sample office rental rates (in dollars per square foot per year) for Los Angeles are shown in the table at the left. Use technology to find the mean rental rate and the sample standard deviation. (Source: LoopNet.com) SOLUTION Minitab, Excel, and the TI-84 Plus each have features that calculate the means and the standard deviations of data sets. Use such technology to find the mean and the standard deviation of the office rental rates. From the displays, you can see that x = 37.1 and s ≈ 15.5. MINITAB Descriptive Statistics: Rental Rates Variable N Mean SE Mean StDev Minimum Rental Rates 30 37.10 2.83 15.48 13.00 Variable Q1 Median Q3 Maximum Rental Rates 26.00 35.00 45.00 72.00 EXCEL TI-84 PLUS 1-Var Stats x=37.1 Σx=1113 Σx2=48245 Sx=15.48380689 sx=15.22355631 Èn=30 A Median Mode Sample Variance Kurtosis Skewness Range Minimum Maximum Sum Count Standard Error B 35 30 239.7483 0.2787 0.689938 59 13 72 1113 30 2.826943 3 4 5 6 7 8 9 10 11 12 13 1 2 Mean 37.1 Standard Deviation 15.48381 Sample Mean Sample Standard Deviation TRY IT YOURSELF 4 Sample office rental rates (in dollars per square foot per year) for Dallas are listed. Use technology to find the mean rental rate and the sample standard deviation. (Adapted from LoopNet.com) 29 27 25 32 14 18 24 26 25 17 15 19 16 19 14 14 13 26 24 20 22 20 14 15 16 38 26 26 25 6 Answer: Page A37 EXAMPLE 4
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