Exam 5: Discrete Random Variables

In the most recent election,19 percent of all eligible college students voted.If a random sample of 20 students were surveyed,find the probability that none of the students voted.

The J.O.Supplies Company buys calculators from a Korean supplier.The probability of a defective calculator is 10 percent.If 3 calculators are selected at random,what is the probability that one of the calculators will be defective?

According to a survey of adults,64 percent have money in a regular savings account.If we were to survey 50 randomly selected adults,find the mean number of adults who would have regular savings accounts.

Consider a Poisson distribution with an average of 3 customers per minute at the local grocery store.If X = the number of arrivals per minute,find the probability of more than 7 customers arriving within a minute.

Consider a Poisson distribution with an average of 3 customers per minute at the local grocery store.If X = the number of arrivals per minute,find the probability of 3 customers arriving within a minute.

If p = .1 and n = 5,then the corresponding binomial distribution is ____________.

According to data from the state blood program,40 percent of all individuals have group A blood.If six individuals give blood,find the probability that none of the individuals has group A blood.

A discrete random variable may assume a countable number of outcome values.

One die is thrown.What is the expected value of the number of dots on the top face of the die?

The J.O.Supplies Company buys calculators from a Korean supplier.The probability of a defective calculator is 10 percent.If 100 calculators are selected at random,what is the standard deviation of the number of defectives?

Three candidates run for different offices in different counties.Each has a one in three chance of being elected in his/her county.What is the probability that at least one of them will be elected?

The probability distribution of a random variable that is defined to be the number of successes obtained in a random sample selected without replacement from a finite population of N elements that contains r successes and N - r failures is:

A car wash loses $30 on rainy days and makes $120 on days when it does not rain.If the probability of rain is 0.15,calculate expected profit for the car wash.

The binomial experiment consists of n independent,identical trials,each of which results in either success or failure and is such that the probability of success on any trial is the same.

A fair die is rolled 10 times.What is the probability that an even number (2,4,or 6)will occur between 2 and 4 times?

If x is a Poisson random variable with a mean of 10,what is the probability that x is greater than 6?

Consider a Poisson distribution with an average of 3 customers per minute at the local grocery store.If X = the number of arrivals per minute,find the expected value of X.

A study conducted by a local university found that 25 percent of college freshmen support increased spending on environmental issues.If 6 college freshmen are randomly selected,find the probability that fewer than 4 support increased spending on environmental issues.

Consider the experiment of tossing a fair coin three times and observing the number of heads that result (X = number of heads).Determine the expected number of heads.

A vaccine is 95 percent effective.What is the probability that it is not effective for one and only one individual out of 20 individuals?