/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q20E Apps not working on smartphones.... [FREE SOLUTION] | 91影视

91影视

Apps not working on smartphones. In a Pew Research Center survey titled U.S. Smartphone Use in 2015, more than 2,000 smartphone users were asked how often the applications (apps) they downloaded on their cell phones were not working correctly. Responses were recorded as follows: 1 = Frequently, 2 = Occasionally, 3 = Rarely, and 4 = Never. The probability distribution for the numerical response, x, is provided in the table.

  1. Verify that the properties of a probability distribution for a discrete random variable are satisfied.
  2. Find P(x>2)
  3. Find E(x). Interpret this value practically.

Short Answer

Expert verified
  1. The total probability is 1, and each of them is between 0 and 1
  2. 0.51
  3. 2.52

Step by step solution

01

(a) Verification of the first property

The first property which needs to be verified is whether the sum of all the properties is equivalent to 1, and this probability distribution verifies that as shown below:

厂耻尘尘补迟颈辞苍鈥塷蹿鈥塼丑别鈥塸谤辞产补产颈濒颈迟颈别蝉=0.10+0.39+0.40+0.11=1

02

Verification of the second property

The second property is that the probabilities must be between 0 and 1, and this distribution showcases that all the probabilities are within that range.Each of the four probabilities is greater than 0 and less than 1.

03

(b) Conditions for probability

The probability distribution must contain probabilities of different values of x, which must lie between 0 and 1. The probabilities of the four responses follow those criteria in this case.

04

Computing the probability

The calculation P(x>2)is shown below:

role="math" localid="1653639865341" P(x>2)=P(x=3)+P(x=4)=0.40+0.11=0.51

Therefore, theP(x>2) is 0.51

05

(c) Formula for calculating E(x)

The formula for calculating E(x)is shown below:

E(x)=厂耻尘尘补迟颈辞苍鈥塷蹿鈥墄辫(x)

Here,X it represents the responses andp(x) represents the associated probabilities.

06

Computing the E(x)

The calculation E(x) is shown below:

E(x)=1脳0.10+2脳0.39+3脳0.40+4脳0.11=0.10+0.78+1.20+0.44=2.52

Therefore, the E(x) is 2.52, which indicates the mean of the responses by taking the associated probabilities of occurrences.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Voltage sags and swells. Refer to the Electrical Engineering (Vol. 95, 2013) study of the power quality of a transformer, Exercise 2.127 (p. 132). Recall that two causes of poor power quality are 鈥渟ags鈥 and 鈥渟wells.鈥. (A sag is an unusual dip, and a swell is an unusual increase in the voltage level of a transformer.) For Turkish transformers built for heavy industry, the mean number of sags per week was 353, and the mean number of swells per week was 184. As in Exercise 2.127, assume the standard deviation of the sag distribution is 30 sags per week, and the standard deviation of the swell distribution is 25 swells per week. Also, assume that the number of sags and number of swells is both normally distributed. Suppose one of the transformers is randomly selected and found to have 400 sags and 100 swells in a week.

a. What is the probability that the number of sags per week is less than 400?

b. What is the probability that the number of swells per week is greater than 100?

Detecting anthrax. Researchers at the University of SouthFlorida Center for Biological Defense have developed asafe method for rapidly detecting anthrax spores in powdersand on surfaces (USF Magazine, Summer 2002). Themethod has been found to work well even when there arevery few anthrax spores in a powder specimen. Considera powder specimen that has exactly 10 anthrax spores.Suppose that the number of anthrax spores in the sampledetected by this method follows an approximate uniformdistribution between 0 and 10.

a. Find the probability that 8 or fewer anthrax spores are detected in the powder specimen.

b. Find the probability that between 2 and 5 anthrax spores are detected in the powder specimen.

Privacy and information sharing. Refer to the Pew Internet & American Life Project Survey (January 2016), Exercise 4.48 (p. 239). The survey revealed that half of all U.S. adults would agree to participate in a free cost-saving loyalty card program at a grocery store, even if the store could potentially sell these data on the customer鈥檚 shopping habits to third parties. In a random sample of 250 U.S. adults, let x be the number who would participate in the free loyalty card program.

a. Find the mean of x. (This value should agree with your answer to Exercise 4.48c.)

b. Find the standard deviation of x.

c. Find the z-score for the value x = 200.

d. Find the approximate probability that the number of the 250 adults who would participate in the free loyalty card program is less than or equal to 200.

Mailrooms contaminated with anthrax. During autumn 2001, there was a highly publicized outbreak of anthrax cases among U.S. Postal Service workers. In Chance (Spring 2002), research statisticians discussed the problem of sampling mailrooms for the presence of anthrax spores. Let x equal the number of mailrooms contaminated with anthrax spores in a random sample of n mailrooms selected from a population of N mailrooms. The researchers showed that the probability distribution for x is given by the formula P(x)=(kx)(N-kn-x)(Nn)

where k is the number of contaminated mailrooms in the population. (In Section 4.4 we identify this probability distribution as the hypergeometric distribution.) Suppose N = 100, n = 3, and k = 20.

a. Find p(0).

b. Find p(1)

. c. Find p(2).

d. Find p(3)

Elevator passenger arrivals. A study of the arrival process of people using elevators at a multilevel office building was conducted and the results reported in Building Services Engineering Research and Technology (October 2012). Suppose that at one particular time of day, elevator passengers arrive in batches of size 1 or 2 (i.e., either 1 or 2 people arrive at the same time to use the elevator). The researchers assumed that the number of batches, n, arriving over a specific time period follows a Poisson process with mean =1.1. Now let xn represent the number of passengers (either 1 or 2) in batch n and assume the batch size has probabilities p=P(xn=1)=0.4andq=P(xn=2)=0.6. Then, the total number of passengers arriving over a specific time period is y=x1+x2+...+xn. The researchers showed that if x1,x2,...xnare independent and identically distributed random variables and also independent of n, then y follows a compound Poisson distribution.

a. Find P(y=0), i.e., the probability of no arrivals during the time period. [Hint: y = 0 only when n = 0.]

b. Find P(y=1), i.e., the probability of only 1 arrival during the time period. [Hint: y = 1 only when n = 1 and x1=1.]

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.