A variable is normally distributed with mean 12 and standard deviation 2. a. Determine the quartiles of the variable. b. Obtain and interpret the 90th percentile. c. Find the value that 65% of all possible values of the variable exceed. d. Find the two values that divide the area under the corresponding normal curve into a middle area of 0.95 and two outside areas of 0.025. Interpret the answer. a. Q1=_____ Q2=_____ Q3=______ (Round to two decimal places as needed.) b. The 90th percentile is__________. (Round to two decimal places as needed.) Choose the correct answer below. A. The 90th percentile is the number that is 90% of the largest data value. B. The 90th percentile is the number that occurs in the data 90% of the time. C. The 90th percentile is the number that divides the bottom 15% of the data from the top 90% of the data. D. The 90th percentile is the number that divides the bottom 90% of the data from the top 15% of the data. c. The value that 65% of all possible values of the variable exceed is_______. (Round to two decimal places as needed.) d. The two values that divide the area under the corresponding normal curve into a middle area of 0.95 and two outside areas of 0.025 are ______and ______. (Round to two decimal places as needed. Use ascending order.) These values enclose the area of the normal curve that is within_____standard deviations. (Round to the nearest integer as needed.)
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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