Many body measurements of people of the same sex and similar ages such as height and upper arm length follow a Normal distribution reasonably closely. Weights, on the other hand, are not Normally distributed. Suppose a survey includes the weights of a representative sample of 548548 females in the United States aged 2020 –2929 . Suppose the mean of the weights was 161.55161.55 pounds, and the standard deviation was 48.9748.97 pounds. The histogram of the data includes a smooth curve representing an ?(161.55,48.97)N(161.55,48.97) distribution. From the histogram, the Normal curve does not appear to follow the pattern in the histogram that closely. Because of this, the use of areas under the Normal curve may not provide a good approximation to weights in various intervals. You may find Table A useful. (a) There were 1313 females that weighed under 100100 pounds. What percent of females aged 2020 to 2929 weighed under 100100 pounds? (Enter your answer rounded to two decimal places.) What percent of the ?(161.55,48.97)N(161.55,48.97) distribution is below 100100 ? (Enter your answer rounded to two decimal places.) (b) There were 3333 females that weighed over 250250 pounds. What percent of females aged 2020 to 2929 weighed over 250250 pounds? (Enter your answer rounded to two decimal places.) What percent of the ?(161.55,48.97)N(161.55,48.97) distribution is above 250250 ? (Enter your answer rounded to two decimal places.)
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!
Many body measurements of people of the same sex and similar ages such as height and upper arm length follow a Normal distribution reasonably closely. Weights, on the other hand, are not
The histogram of the data includes a smooth curve representing an ?(161.55,48.97)N(161.55,48.97) distribution.
From the histogram, the Normal curve does not appear to follow the pattern in the histogram that closely. Because of this, the use of areas under the Normal curve may not provide a good approximation to weights in various intervals.
You may find Table A useful.
(a) There were 1313 females that weighed under 100100 pounds. What percent of females aged 2020 to 2929 weighed under 100100 pounds? (Enter your answer rounded to two decimal places.)
What percent of the ?(161.55,48.97)N(161.55,48.97) distribution is below 100100 ? (Enter your answer rounded to two decimal places.)
(b) There were 3333 females that weighed over 250250 pounds. What percent of females aged 2020 to 2929 weighed over 250250 pounds? (Enter your answer rounded to two decimal places.)
What percent of the ?(161.55,48.97)N(161.55,48.97) distribution is above 250250 ? (Enter your answer rounded to two decimal places.)
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