Choosing portable grill displays. Refer to the Journal of Consumer Research (Mar. 2003) marketing study of influencing consumer choices by offering undesirable alternatives, Exercise 3.109 (p. 204). Recall that each of 124 college students selected showroom displays for portable grills. Five different displays (representing five different-sized grills) were available. Still, the students were instructed to select only three displays to maximize purchases of Grill #2 (a smaller-sized grill). The table shows the grill display combinations and the number of times each was selected by the 124 students. Suppose one of the 124 students is selected at random. Let x represent the sum of the grill numbers selected by this student. (This value indicates the size of the grills selected.)

a. Find the probability distribution for x.

b. What is the probability that x exceeds 10?

Short Answer

Expert verified

a.

b. 0.89

Step by step solution

01

(a) Definition of probability distribution in this context

The probability distribution in this context refers to the possibility of a particular grill combination getting selected out of all the grill combinations. The associated probabilities for a particular combination to get selected are given in the chart below.

02

Calculation of the probability distribution

The calculation of the associated probabilities is shown below:

03

(b) Formula for computing P(x>10)

The formula for calculating P(x>10)is shown below:

P(x>10)=P(x=35)+P(x=42)+P(x=34)

The P(x>10)indicates the probability of selecting a grill display combination by more than 10 students.

04

Computing the P(x>10)

The calculation of the probability of selecting x more than 10 students is calculated below:

P(x>10)=35124+42124+34124=0.28+0.34+0.27=0.89

It P(x>10) is found to be 0.89.

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Most popular questions from this chapter

Soft-drink dispenser. The manager of a local soft-drink bottling company believes that when a new beverage dispensing machine is set to dispense 7 ounces, it in fact dispenses an amount at random anywhere between 6.5and 7.5 ounces inclusive. Suppose has a uniform probability

distribution.

a.Is the amount dispensed by the beverage machine a discreteor a continuous random variable? Explain.

b. Graph the frequency function forX , the amount of beverage the manager believes is dispensed by the new machine when it is set to dispense 7 ounces.

c. Find the mean and standard deviation for the distribution graphed in part b, and locate the mean and theinterval μ±2σon the graph.

d. Find P(x7).

e. FindP(x<6) .

f. FindP(6.5x7.25) .

g. What is the probability that each of the next six bottles filled by the new machine will contain more than7.25 ounces of beverage? Assume that the amount of beverage dispensed in one bottle is independent of the amount dispensed in another bottle.

Detecting a computer virus attack. Chance (Winter 2004) presented basic methods for detecting virus attacks (e.g.,Trojan programs or worms) on a network computer that are sent from a remote host. These viruses reach the network through requests for communication (e.g., e-mail, Web chat, or remote log-in) that are identified as “packets.” For example, the “SYN flood” virus ties up the network computer by “flooding” the network with multiple packets. Cyber security experts can detect this type of virus attack if at least one packet is observed by a network sensor. Assume that the probability of observing a single packet sent from a new virus is only .001. If the virus actually sends 150 packets to a network computer, what is the probability that the virus is detected by the sensor?

Suppose x is a binomial random variable with p = .4 and n = 25.

a. Would it be appropriate to approximate the probability distribution of x with a normal distribution? Explain.

b. Assuming that a normal distribution provides an adequate approximation to the distribution of x, what are the mean and variance of the approximating normal distribution?

c. Use Table I in Appendix D to find the exact value of P(x9).

d. Use the normal approximation to find P(x9).

If x is a binomial random variable, calculate , , and for each of the following:

  1. n = 25, p = .5
  2. n = 80, p = .2
  3. n = 100, p = .6
  4. n = 70, p = .9
  5. n = 60, p = .8
  6. n = 1000, p = .04

Checkout lanes at a supermarket. A team of consultants working for a large national supermarket chain based in the New York metropolitan area developed a statistical model for predicting the annual sales of potential new store locations. Part of their analysis involved identifying variables that influence store sales, such as the size of the store (in square feet), the size of the surrounding population, and the number of checkout lanes. They surveyed 52 supermarkets in a particular region of the country and constructed the relative frequency distribution shown below to describe the number of checkout lanes per store, x.

a. Why do the relative frequencies in the table represent the approximate probabilities of a randomly selected supermarket having x number of checkout lanes?

b. FindE(x) and interpret its value in the context of the problem.

c. Find the standard deviation of x.

d. According to Chebyshev’s Rule (Chapter 2, p. 106), what percentage of supermarkets would be expected to fall withinμ±σ? withinμ±2σ?

e. What is the actual number of supermarkets that fall within? ? Compare your answers with those of part d. Are the answers consistent?

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