1.
The Environmental Department monitors sulphur dioxide (SO2) emission of ABC
powerplant every hour. Assume the concentration of SO2 from ABC powerplant is normal
distributed. The powerplant claims that the average SO2 emission is 75 ppb (parts per
billion) and the standard deviation is 0.75 ppb. The Environmental Department set the
standard of SO2 concentration for all powerplants is 77 ppb.
(a)
There are randomly selected 11 powerplants in this country with mean of 75.2 ppb and standard deviation of 0.4 ppb.
(i)Construct a 90% confidence interval for the population mean and interpret the result.
(ii)Determine the assumption in a(i).