A new formula for estimating the water evaporation from occupied swimming pools was proposed and analyzed in the journal, Heating/ Piping/Air Conditioning Engineering (Apr. 2013). The key components of the new formula are number of pool occupants, area of pool’s water surface, and the density difference between room air temperature and the air at the pool’s surface. Data were collected from a wide range of pools where the evaporation level was known. The new formula was applied to each pool in the sample, yielding an estimated evaporation level. The absolute value of the deviation between the actual and estimated evaporation level was then recorded as a percentage. The researchers reported the following summary statistics for absolute deviation percentage: y̅ = 18, s = 20. Assume that the sample contained  n = 500 swimming pools. 

a. Estimate the true mean absolute deviation percentage for the new formula with a 90% confidence interval. 

b. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) handbook also provides a formula for estimating pool evaporation. Suppose the ASHRAE mean absolute deviation percentage is μ = 34%. (This value was reported in the article.) On average, is the new formula “better” than the ASHRAE formula? Explain.