Chapter 7: Problem 56
Suppose that \(20 \%\) of the 10,000 signatures on a certain recall petition are invalid. Would the number of invalid signatures in a sample of 2000 of these signatures have (approximately) a binomial distribution? Explain.
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Chapter 7: Problem 56
Suppose that \(20 \%\) of the 10,000 signatures on a certain recall petition are invalid. Would the number of invalid signatures in a sample of 2000 of these signatures have (approximately) a binomial distribution? Explain.
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Suppose that \(20 \%\) of all homeowners in an earthquake-prone area of California are insured against earthquake damage. Four homeowners are selected at random; let \(x\) denote the number among the four who have earthquake insurance. a. Find the probability distribution of \(x\). (Hint: Let \(S\) denote a homeowner who has insurance and \(\mathrm{F}\) one who does not. Then one possible outcome is SFSS, with probability \((.2)(.8)(.2)(.2)\) and associated \(x\) value of \(3 .\) There are 15 other outcomes.) b. What is the most likely value of \(x\) ? c. What is the probability that at least two of the four selected homeowners have earthquake insurance?
Starting at a particular time, each car entering an intersection is observed to see whether it turns left (L) or right (R) or goes straight ahead (S). The experiment terminates as soon as a car is observed to go straight. Let \(y\) denote the number of cars observed. What are possible \(y\) values? List five different outcomes and their associated \(y\) values.
According to the paper "Commuters' Exposure to Particulate Matter and Carbon Monoxide in Hanoi. Vietnam" (Transportation Research [2008]: 206-211), the carbon monoxide exposure of someone riding a motorbike for \(5 \mathrm{~km}\) on a highway in Hanoi is approximately normally distributed with a mean of \(18.6\) ppm. Suppose that the standard deviation of carbon monoxide exposure is \(5.7\) ppm. Approximately what proportion of those who ride a motorbike for \(5 \mathrm{~km}\) on a Hanoi highway will experience a carbon monoxide exposure of more than 20 ppm? More than 25 ppm?
Let \(x\) be the number of courses for which a randomly selected student at a
certain university is registered. The probability distribution of \(x\) appears
in the following table:
$$
\begin{array}{cccccccc}
x & 1 & 2 & 3 & 4 & 5 & 6 & 7 \\
p(x) & .02 & .03 & .09 & .25 & .40 & .16 & .05
\end{array}
$$
a. What is \(P(x=4)\) ?
b. What is \(P(x \leq 4)\) ?
c. What is the probability that the selected student is taking at most five
courses?
d. What is the probability that the selected student is taking at least five
courses? more than five courses?
e. Calculate \(P(3 \leq x \leq 6)\) and \(P(3
The size of the left upper chamber of the heart is one measure of cardiovascular health. When the upper left chamber is enlarged, the risk of heart problems is increased. The paper "Left Atrial Size Increases with Body Mass Index in Children" (International Journal of Cardiology [2009]: 1-7) described a study in which the left atrial size was measured for a large number of children age 5 to 15 years. Based on this data, the authors concluded that for healthy children, left atrial diameter was approximately normally distributed with a mean of \(26.4 \mathrm{~mm}\) and a standard deviation of \(4.2 \mathrm{~mm}\). a. Approximately what proportion of healthy children has left atrial diameters less than \(24 \mathrm{~mm}\) ? b. Approximately what proportion of healthy children has left atrial diameters greater than \(32 \mathrm{~mm}\) ? c. Approximately what proportion of healthy children has left atrial diameters between 25 and \(30 \mathrm{~mm}\) ? d. For healthy children, what is the value for which only about \(20 \%\) have a larger left atrial diameter?
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