A sample of bridge and tunnel officers has an average exam score of 89, with a standard deviation of 4.5. If the exam score is normally distributed, what percentage of the bridge and tunnel officers have exam scores? Z Scores Area less than 78 -1.90 58.0% less than 69 more than 87 more than 95 between 89 and 99 between 75 and 90
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!
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