Mobile homes are tightly constructed for energy conservation. This can lead to a buildup of indoor pollutants. The paper “A Survey of Nitrogen Dioxide Levels Inside Mobile Homes” (Journal of the Air Pollution Control Association [1988]: 647– 651) discussed various aspects of NO2 concentration in these structures.
a. In one sample of mobile homes in the Los Angeles area, the mean NO2 concentration in kitchens during the summer was 36.92 ppb, and the standard deviation was 11.34. Making no assumptions about the shape of the NO2 distribution, what can be said about the percentage of observations between 14.24 and 59.60?
b. Inside what interval is it guaranteed that at least 89% of the concentration observations will lie?
c. In a sample of non– Los Angeles mobile homes, the average kitchen NO2 concentration during the winter was 24.76 ppb, and the standard deviation was 17.20. Do these values suggest that the histogram of sample observations did not closely resemble a normal curve?