Suppose the heights of 18-year-old men are approximately normally distributed, with mean 69 inches and standard deviation 5 inches. (a) What is the probability that an 18-year-old man selected at random is between 68 and 70 inches tall? (Round your answer to four decimal places.) a 0.0793 b 0.1585 c 0.0317 d 0.1744 (b) If a random sample of sixteen 18-year-old men is selected, what is the probability that the mean height x is between 68 and 70 inches? (Round your answer to four decimal places.) a 0.1153 b 0.5187 c 0.5763 d 0.6339 (c) Compare your answers to parts (a) and (b). Is the probability in part (b) much higher? Why would you expect this? a The probability in part (b) is much lower because the standard deviation is smaller for the x distribution. b The probability in part (b) is much higher because the mean is smaller for the x distribution. c The probability in part (b) is much higher because the standard deviation is smaller for the x distribution. d The probability in part (b) is much higher because the standard deviation is larger for the x distribution
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!
Suppose the heights of 18-year-old men are approximately
(b) If a random sample of sixteen 18-year-old men is selected, what is the probability that the mean height x is between 68 and 70 inches? (Round your answer to four decimal places.)
(c) Compare your answers to parts (a) and (b). Is the probability in part (b) much higher? Why would you expect this?
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