Gestation Period The lengths of human pregnancies are approximately normally distributed, with mean m = 266 days and standard deviation s = 16 days. (a) What proportion of pregnancies lasts more than 270 days? (b) What proportion of pregnancies lasts less than 250 days? (c) What proportion of pregnancies lasts between 240 and 280 days?
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!
Gestation Period The lengths of human pregnancies are approximately
(a) What proportion of pregnancies lasts more than 270 days? (b) What proportion of pregnancies lasts less than 250 days? (c) What proportion of pregnancies lasts between 240 and
280 days?
(d) What is the probability that a randomly selected pregnancy
lasts more than 280 days?
(e) What is the probability that a randomly selected pregnancy
lasts no more than 245 days?
(f) A “very preterm” baby is one whose gestation period is less
than 224 days. Are very preterm babies unusual?
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