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Chapter 5: Q2 (page 195)
Is the random variable given in the accompanying table discreteor continuous? Explain.
Number of Girls x | P(x) |
0 | 0.063 |
1 | 0.25 |
2 | 0.375 |
3 | 0.25 |
4 | 0.063 |
The variable x is a discrete random variable.
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Currently, an average of 7 residents of the village of Westport (population 760) die each year (based on data from the U.S. National Center for Health Statistics).
a. Find the mean number of deaths per day.
b. Find the probability that on a given day, there are no deaths.
c. Find the probability that on a given day, there is more than one death.
d. Based on the preceding results, should Westport have a contingency plan to handle more than one death per day? Why or why not?
In Exercises 21鈥�24, assume that when adults with smartphones are randomly selected, 54% use them in meetings or classes (based on data from an LG Smartphone survey).
If 8 adult smartphone users are randomly selected, find the probability that exactly 6 of them use their smartphones in meetings or classes.
In Exercises 21鈥�25, refer to the accompanying table, which describes the numbers of adults in groups of five who reported sleepwalking (based on data from 鈥淧revalence and Comorbidity of Nocturnal Wandering In the U.S. Adult General Population,鈥� by Ohayon et al., Neurology, Vol. 78, No. 20).
Find the mean and standard deviation for the numbers of sleepwalkers in groups of five.
x | P(x) |
0 | 0.172 |
1 | 0.363 |
2 | 0.306 |
3 | 0.129 |
4 | 0.027 |
5 | 0.002 |
In Exercises 15鈥�20, assume that random guesses are made for eight multiple choice questions on an SAT test, so that there are n = 8 trials, each with probability of success (correct) given by p = 0.20. Find the indicated probability for the number of correct answers.
Find the probability that the number x of correct answers is at least 4.
In a USA Todaypoll, subjects were asked if passwords should be replaced with biometric security, such as fingerprints. The results from that poll have been used to create the accompanying table. Does this table describe a probability distribution? Why or why not?
Response | P(x) |
Yes | 0.53 |
No | 0.17 |
Not Sure | 0.3 |
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