Exam 2: Probability Concepts and Applications

Assume you have a normal distribution representing the likelihood of completion times.The mean of this distribution is 10,and the standard deviation is 3.The probability of completing the project in 8 or fewer days is the same as the probability of completing the project in 18 days or more.

The number of cell phone minutes used by high school seniors follows a normal distribution with a mean of 500 and a standard deviation of 50.What is the probability that a student uses between 400 and 500 minutes?

The classical method of determining probability is

Which distribution is helpful in testing hypotheses about variances?

A dry cleaning business offers a pick-up and delivery service for a 10 percent surcharge.Management believes 60 percent of customers will take advantage of this service.They are also considering offering customers the option of opening an account and receiving monthly bills.They believe 60 percent of their customers (regardless of whether or not they use the pick-up service)will use the account service.If the two services are introduced to the market,what is the probability a customer uses both services?

A market research study is being conducted to determine if a product modification will be well received by the public.A total of 1,000 consumers are questioned regarding this product. The table below provides information regarding this sample. (a)What is the probability that a randomly selected male would find this change unfavorable (negative)? (b)What is the probability that a randomly selected person would be a female who had a positive reaction? (c)If it is known that a person had a negative reaction to the study,what is the probability that the person is male?

A company is considering producing some new Gameboy electronic games.Based on past records,management believes that there is a 70 percent chance that each of these will be successful,and a 30 percent chance of failure.Market research may be used to revise these probabilities.In the past,the successful products were predicted to be successful based on market research 90 percent of the time.However,for products that failed,the market research predicted these would be successes 20 percent of the time.If market research is performed for a new product,what is the probability that the product will be successful if the market research indicates a success?

In a normal distribution,the Z value represents the number of standard deviations from a value X to the mean.

Fast Service Store has maintained daily sales records on the various size "Cool Drink" sales. Assuming that past performance is a good indicator of future sales, (a)What is the probability of a customer purchasing a $1.00 "Cool Drink?" (b)What is the probability of a customer purchasing a $1.25 "Cool Drink?" (c)What is the probability of a customer purchasing a "Cool Drink" that costs greater than or equal to $1.00? (d)What is the expected value of a "Cool Drink"? (e)What is the variance of a "Cool Drink"?

Assume that you have an urn containing 10 balls of the following description: 4 are white (W)and lettered (L) 2 are white (W)and numbered (N) 3 are yellow (Y)and lettered (L) 1 is yellow (Y)and numbered (N) If you draw a numbered ball (N),the probability that this ball is white (W)is 0.60.

Data for a particular subdivision near downtown Houston indicate that the average price per square foot for a home is $100 with a standard deviation of $5 (normally distributed).What is the probability that the average price per square foot for a home is greater than $110?

The number of defects that occur per unit of product follows a Poisson distribution with a mean of 4 defects per unit.What is the standard deviation of this distribution?

Drivers arrive at a toll booth at a rate of 3 per minute during peak traffic periods.The time between consecutive driver arrivals follows an exponential distribution.What is the probability that it will take less than 1/2 of a minute between consecutive drivers?

Given two statistically dependent events (A,B),the conditional probability of P(A|B)= P(B)/P(AB).

The F statistic is the ratio of two sample standard deviations from independent normal distributions.

A discrete random variable has a mean of 400 and a variance of 64.What is the standard deviation?

List the parameter(s)of the Poisson distribution.

The time required to complete a project is normally distributed with a mean of 80 weeks and a standard deviation of 10 weeks.The construction company must pay a penalty if the project is not finished by the due date in the contract.If a construction company bidding on this contract wishes to be 90 percent sure of finishing by the due date,what due date (project week #)should be negotiated?

Suppose that 10 golfers enter a tournament and that their respective skill levels are approximately the same.Six of the entrants are female and two of those are older than 40 years old.Three of the men are older than 40 years old.What is the probability that the winner will be either female or older than 40 years old?

Stating that two events are statistically independent means that the probability of one event occurring is independent of the probability of the other event having occurred.