In a certain suburb of Montréal, residents have expressed their worries about the quality of the air. Of particular concern is the concentration (in μg/m3) of particulate matter smaller than 2.5 μm in size (PM2.5). The environmental standard is a PM2.5 concentration of 15 μg/m3 or less. Part A: To conduct this study, Thomas installs 25 PM2.5 detectors at different locations in the suburban area. Each detector will provide one reading of PM2.5 concentration at a given time. With 25 detectors, what is the probability that Thomas declares the sample mean of PM2.5 concentrations significantly greater than the environmental standard while the population means is 16 μg/m3? The population variance is assumed to be known and equal to 9. Use α = 0.01. Part 2: Thomas is interested to purchase a new and cheaper instrument to measure PM2.5 concentration. He is worried, however, that the precision of the new instrument may be lower than that of the current one. To be acceptable, the standard deviation of measurements made with the new instrument should not exceed 5 μg/m3. To assess whether he could reliably use the new instrument, Thomas makes 10 readings of an air sample with known concentration of PM2.5. From the data, he calculates a sample standard deviation of 7 μg/m3. Is the variability in the 10 readings made with the new instrument acceptable? Use α = 0.05.
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
In a certain suburb of Montréal, residents have expressed their worries about the quality of the air. Of particular concern is the concentration (in μg/m3) of particulate matter smaller than 2.5 μm in size (PM2.5). The environmental standard is a PM2.5 concentration of 15 μg/m3 or less.
Part A: To conduct this study, Thomas installs 25 PM2.5 detectors at different locations in the suburban area. Each detector will provide one reading of PM2.5 concentration at a given time. With 25 detectors, what is the
Part 2: Thomas is interested to purchase a new and cheaper instrument to measure PM2.5 concentration. He is worried, however, that the precision of the new instrument may be lower than that of the current one. To be acceptable, the standard deviation of measurements made with the new instrument should not exceed 5 μg/m3. To assess whether he could reliably use the new instrument, Thomas makes 10 readings of an air sample with known concentration of PM2.5. From the data, he calculates a sample standard deviation of 7 μg/m3. Is the variability in the 10 readings made with the new instrument acceptable? Use α = 0.05.
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