Business Stats Exam 2

A simple random sample of 100 observations was taken from a large population. The sample mean and the standard deviation were determined to be 80 and 12 respectively. The standard error of the mean is

1.20

The number of customers that enter a store during one day is an example of

a discrete random variable

The union of events A and B is the event containing

all the sample points belonging to A or B or both

A theorem that allows us to use the normal probability distribution to approximate the sampling distribution of sample means and sample proportions whenever the sample size is large is known as the

central limit theorem

. The probability that a continuous random variable takes any specific value

is equal to zero

The probability of the intersection of two mutually exclusive events

must always be equal to 0

The purpose of statistical inference is to provide information about the

population based upon information contained in the sample

Initial estimates of the probabilities of events are known as _____ probabilities.

prior

The key difference between the binomial and hypergeometric distribution is that, with the hypergeometric distribution the

probability of success changes from trial to trial.

A numerical description of the outcome of an experiment is called a

random variable

The standard deviation of all possible values is called the

standard error of the mean

As the sample size increases, the

standard error of the mean decreases

On a December day, the probability of snow is .30. The probability of a "cold" day is .50. The probability of snow and "cold" weather is .15. Are snow and "cold" weather independent events?

yes

The sample mean is the point estimator of

μ

In a binomial experiment the probability of success is 0.06. What is the probability of two successes in seven trials?

0.0555

The number of electrical outages in a city varies from day to day. Assume that the number of electrical outages (x) in the city has the following probability distribution. x f(x) 0 0.80 1 0.15 2 0.04 3 0.01 The mean and the standard deviation for the number of electrical outages (respectively) are

0.26 and 0.577

If A and B are independent events with P(A) = 0.65 and P(A Ç B) = 0.26, then, P(B) =

0.400

If P(A) = 0.4, P(B | A) = 0.35, P(A È B) = 0.69, then P(B) =

0.43

The random variable x is known to be uniformly distributed between 70 and 90. The probability of x having a value between 80 to 95 is

0.5

Events A and B are mutually exclusive with P(A) = 0.3 and P(B) = 0.2. Then, P(Bc) =

0.8

X is a normally distributed random variable with a mean of 8 and a standard deviation of 4. The probability that X is between 1.48 and 15.56 is

0.9190

The life expectancy of a particular brand of tire is normally distributed with a mean of 40,000 and a standard deviation of 5,000 miles. What is the probability that a randomly selected tire will have a life of at least 30,000 miles?

0.9772

Given that Z is a standard normal random variable, what is the probability that Z -2.12?

0.9830

Assume that you have a binomial experiment with p = 0.4 and a sample size of 50. The variance of this distribution is

12

A population has a mean of 75 and a standard deviation of 8. A random sample of 800 is selected. The expected value of is

75

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

Poisson distribution