Econ Chapter 5

In a binomial experiment the probability of success is 0.05. What is the probability of two successes in seven trials? a. 0.0036 b. 0.0000 c. 0.0406 d. 0.3667

c. 0.0406

To compute the probability that in a random sample of n elements, selected without replacement, we will obtain x successes, we would use the _____ probability distribution. a. binomial b. Poisson c. hypergeometric d. exponential

c. hypergeometric

Random variable x has the probability function f(x) = X/6, for x = 1, 2 or 3​ The expected value of x is a. 0.333. b. 0.500. c. 2.000. d. 2.333.

d. 2.333.

The mean number of pages per day written by an author is 27. What is the probability this author writes 33 pages on a particular day? Assume a Poisson distribution for this scenario. a. 0.0372. b. 0.9628. c. 0.4277. d. 0.9572.

a. 0.0372.

Forty-four percent of all registered voters in a national election are female. A random sample of 5 voters is selected. The probability that there are no females in the sample is a. 0.0551. b. 0.9450. c. 0.4400. d. 0.1649.

a. 0.0551.

The random variable x is the number of occurrences of an event over an interval of ten minutes. It can be assumed that the probability of an occurrence is the same in any two time periods of an equal length. It is known that the mean number of occurrences in ten minutes is 5.3. The appropriate probability distribution for the random variable is a. discrete. b. continuous. c. either discrete or continuous depending on how the interval is defined. d. binomial.

a. discrete.

Three percent of the customers of a mortgage company default on their payments. A sample of five customers is selected. What is the probability that exactly two customers in the sample will default on their payments? a. 0.0003 b. 0.0082 c. 0.0077 d. 0.0008

b. 0.0082

Which of the following is a characteristic of an experiment where the binomial probability distribution is applicable? a. The experiment has at least two possible outcomes. b. Exactly two outcomes are possible on each trial. c. The trials are dependent on each other. d. The probabilities of the outcomes changes from one trial.

b. Exactly two outcomes are possible on each trial.

The key difference between the binomial and hypergeometric distribution is that, with the hypergeometric distribution the a. probability of success must be less than 0.5, b. probability of success changes from trial to trial. c. trials are independent of each other. d. random variable is continuous.

b. probability of success changes from trial to trial.

Which of the following is a required condition for a discrete probability function? a. f(x) 0 for all values of x b. ∑f(x) = 1 for all values of x c. ∑f(x) = 0 for all values of x d. ∑f(x) 1 for all values of x

b. ∑f(x) = 1 for all values of x

The probability that Pete will catch fish when he goes fishing is .88. Pete is going to fish 3 days next week. Define the random variable x to be the number of days Pete catches fish. The probability that Pete will catch fish on one day or less is a. 0.880. b. 0.038. c. 0.040. d. 0.960.

c. 0.040.

The random variable x is the number of occurrences of an event over an interval of ten minutes. It can be assumed that the probability of an occurrence is the same in any two time periods of an equal length. It is known that the mean number of occurrences in ten minutes is 5.3. The probability that there are less than 3 occurrences is a. 0.0659. b. 0.0948. c. 0.1016. d. 0.1239.

c. 0.1016.

A binomial probability distribution with p = .3 is a. negatively skewed. b. symmetric. c. positively skewed. d. multi-modal.

positively skewed.

In the textile industry, a manufacturer is interested in the number of blemishes or flaws occurring in each 100 feet of material. The probability distribution that has the greatest chance of applying to this situation is the _____ distribution. a. normal b. binomial c. Poisson d. uniform

Poisson

The expected value of a discrete random variable a. is the most likely or highest probability value for the random variable. b. will always be one of the values x can take on, although it may not be the highest probability value for the random variable. c. is the average value for the random variable over many repeats of the experiment. d. is the value it is expected to assume in the next trial.

*c. is the average value for the random variable over many repeats of the experiment.

Twenty percent of the students in a class of 400 are planning to go to graduate school. The standard deviation of this binomial distribution is a. 20. b. 64. c. 8. d. 40.

8

In a binomial experiment consisting of five trials, the number of different values that x (the number of successes) can assume is a. 2. b. 5. c. 6. d. 10.

6

When dealing with the number of occurrences of an event over a specified interval of time or space, the appropriate probability distribution is a _____ distribution. a. binomial b. Poisson c. normal d. hypergeometric probability

Poisson

The variance Var(x) for the binomial distribution is given by equation a. np(n - 1). b. np(1 - np). c. n(1 - p). d. np(1 - p).

d. np(1 - p).