Suggested Strategy: Since you will have approximately 1.5 minutes for each question and this question appears very calculation intensive, it is likely that there is a “trick.” Here, start with the apartment building because the labor-intensive part of the calculation has been completed.  Remember that the standard deviation is the square root of the variance and that both the formula for the population variance and the formula for the sample variance have the same numerator (the sum of the squared result of the observation less the mean). The denominator of the population variance is the entire data set n, (5 here). The denominator of the sample variance is n-1, (or 4 here).

Thus, the population variance = (the sum of the square result of the observation less the mean) / number of observations.  Here, 15.76 = x / 5, x = 78.80.

So, the sample variance = 78.80 / 4 = 19.70, and the sample standard deviation = 19.70^1/2 = 4.44%.

Both remaining statements are incorrect. FYI, the calculations for the REIT are as follows:

• Mean = (15 + 8 + 13 + 9 + 13) / 5 = 11.6
• (The sum of the observation less the mean)² = [(15-11.6)² + (8 – 11.6)² + (13 – 11.6)² + (9 – 11.6)² + (13 – 11.6)²]  = 35.2
• The population standard deviation = [(35.2 / 5.0)]^1/2 = [7.04]^1/2 = 2.65%
• The sample standard deviation = [(35.2 / 4.0)]^1/2 = [8.80]^1/2 = 2.97%