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Chapter 5: Q 3 (page 220)
Are the values found in Exercise 2 statistics or parameters? Why?
The values are parameters.
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In Exercises 7鈥�14, determine whether a probability
distribution is given. If a probability distribution is given, find its mean and standard deviation. If a probability distribution is not given, identify the requirements that are not satisfied.
A sociologist randomly selects single adults for different groups of three, and the random variable xis the number in the group who say that the most fun way to flirt is in person(based on a Microsoft Instant Messaging survey).
x | P(x) |
0 | 0.091 |
1 | 0.334 |
2 | 0.408 |
3 | 0.166 |
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 = eight 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 fewer than 3.
Groups of people aged 15鈥�65 are randomly selected and arranged in groups of six. The random variable xis the number in the group who say that their family and / or partner contribute most to their happiness (based on a Coca-Cola survey). The accompanying table lists
the values of xalong with their corresponding probabilities. Does the table describe a probability distribution? If so, find the mean and standard deviation.
x | P(x) |
0 | 0+ |
1 | 0.003 |
2 | 0.025 |
3 | 0.111 |
4 | 0.279 |
5 | 0.373 |
6 | 0.208 |
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).
Using Probabilities for Identifying Significant Events
a.Find the probability of getting exactly 4 sleepwalkers among 5 adults.
b. Find the probability of getting 4 or more sleepwalkers among 5 adults.
c. Which probability is relevant for determining whether 4 is a significantly highnumber of sleepwalkers among 5 adults: the result from part (a) or part (b)?
d. Is 4 a significantly high number of sleepwalkers among 5 adults? Why
or why not?
x | P(x) |
0 | 0.172 |
1 | 0.363 |
2 | 0.306 |
3 | 0.129 |
4 | 0.027 |
5 | 0.002 |
In Exercises 6鈥�10, use the following: Five American Airlines flights are randomly selected, and the table in the margin lists the probabilities for the number that arrive on time (based on data from the Department of Transportation). Assume that five flights are randomly selected.
What does the probability of 0+ indicate? Does it indicate that among five randomly selectedflights, it is impossible for none of them to arrive on time?
x | P(x) |
0 | 0+ |
1 | 0.006 |
2 | 0.051 |
3 | 0.205 |
4 | 0.409 |
5 | 0.328 |
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