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" 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 38.84 ppb, and the standard deviation was 11.44. Making no assumptions about the shape of the NO2 distribution, what can be said about the percentage of observations between 15.96 and 61.72? (Round the answer to the nearest whole number.)
At least _____________% (I got 95% but this is wrong)
(b) Inside what interval is it guaranteed that at least 89% of the concentration observations will lie?
[or ( ______,______ ] or )