Chapter 6: Problem 3
Calculate the area under the standard normal curve to the left of these values: a. \(z=1.6\) b. \(z=1.83\) c. \(z=.90\) d. \(z=4.18\)
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Chapter 6: Problem 3
Calculate the area under the standard normal curve to the left of these values: a. \(z=1.6\) b. \(z=1.83\) c. \(z=.90\) d. \(z=4.18\)
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How often do you watch movies at home? A USA Today Snapshot found that about 7 in 10 adults say they watch movies at home at least once a week. \(^{5}\) Suppose a random sample of \(n=50\) adults are polled and asked if they had watched a movie at home this week. Let us assume that \(p=.7\) is, in fact, correct. What are the probabilities for the following events? a. Fewer than 30 individuals watched a movie at home this week? b. More than 42 individuals watched a movie at home this week? c. Fewer than 10 individuals did not watch a movie at home this week?
a. Find the probability that \(z\) is greater than \(-.75 .\) b. Find the probability that \(z\) is less than 1.35 .
Let \(x\) be a binomial random variable with \(n=25\) and \(p=.3\) a. Is the normal approximation appropriate for this binomial random variable? b. Find the mean and standard deviation for \(x\). c. Use the normal approximation to find \(P(6 \leq x \leq 9)\). d. Use Table 1 in Appendix I to find the exact probability \(P(6 \leq x \leq 9)\). Compare the results of parts \(c\) and d. How close was your approximation?
Human heights are one of many biological random variables that can be modeled by the normal distribution. Assume the heights of men have a mean of 69 inches with a standard deviation of 3.5 inches. a. What proportion of all men will be taller than \(6^{\prime} 0^{\prime \prime}\) ? (HINT: Convert the measurements to inches.) b. What is the probability that a randomly selected man will be between \(5^{\prime} 8^{\prime \prime}\) and \(6^{\prime} 1^{\prime \prime}\) tall? c. President George \(\mathrm{W}\). Bush is \(5^{\prime} 11^{\prime \prime}\) tall. Is this an unusual height? d. Of the 42 presidents elected from 1789 through 2006,18 were \(6^{\prime} 0^{\prime \prime}\) or taller. \(^{1}\) Would you consider this to be unusual, given the proportion found in part a?
A normal random variable \(x\) has mean \(\mu=10\) and standard deviation
\(\sigma=2\). Find the probabilities of these \(x\) -values:
a. \(x>13.5\)
b. \(x<8.2\)
c. \(9.4
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