Quantitative Analysis - Test 1

Assume z is a standard normal random variable. Then P(-1.96 </ z </ -1.4) equals =

0.0558

The random variable x is the number of occurences of an event over an interval of 10 minutes. It can be assumed 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 10. minutes is 5.3. What is the probability there are 8 occurrences in 10 minutes.

.0731

Four percent of the customers of a mortgage company default on their payments. A sample of five customers is selected. What is the probability that two or more customers in the sample will default on their payments?

0.014

The empirical rule states that, for data having a bell-shaped distribution, the portion of data values being within one standard deviation of the mean is approx.

68%

A normal probability distribution can be either continuous or discrete.

False

A probability sampling method in which we randomly select one of the first k elements and then select every kth element thereafter is known as cluster sampling.

False

A social security number is an example of the interval scale of measurement

False

For any continuous random variable, the probability that the random variable takes on exactly a specific value is any value between 0 and 1.

False

Statistical studies in which researchers control variables of interest are known as observational studies.

False

The player's number on a baseball uniform is an example of quantitative variable.

False

The number of hours worked (per week) by 400 statistics students are shown below. Number of hours: Frequency: 0 </= x < 10 20 10 </= x < 20 80 20 </= x <30 200 30 </= x <40 100 The class width for this distribution is 9.

False.

In a binomial experiment, the probability of success does not change from trial to trial

true

Suppose we flip a fair coin five times and each time it lands heads up. The probability of landing heads up on the next flip is 0.5.

true

x is a random variable with the probability function: f(x):x/6 for x= 1,2, or 3. The expected value of x is 2.33.

true

If you are conducting an experiment where the probability of a success is .02 and you are interested in the probability of two successes in 15 trials, the correct probability function to use is the Poisson distribution

false

To apply the addition rule, the events must be mutually exclusive

false

A shipment to a drugstore contained a package of 20 toothbrushes (for sale individually). The package of 20 toothbrushes contained 3 that were defective (so 17 were not defective). What is the probability the first two toothbrushes sold from this package of 20 will both be defective?

(3/20) x (2/19) = 0.0158

Assume z is a standard normal random variable. What is the value of z if the area to the right of z is .9803?

-2.06

Assume z is a standard normal random variable. The P(z >/ 2.11) equals

.0174

The starting salaries of individuals with an MBA degree are normally distributed with a mean of $40,000 and a standard deviation of $5,000. What is the probability that MBAs will have starting salaries of $34,000 to $46,000?

.7698

For a standard normal distribution, the probability of z </ o is

0.5

If P(A) = .75, P(A u B) = .86, and P(A n B) = .56, then P(B) =

0.67

Of five letters, (A, B, C, D, and E), two letters are to be selected at random. How many possible selections are there?

10

Use data in #11, what is the sample standard deviation for the time spent watching tv?

13.5

A simple random sample of 64 observations was taken from a large population. The population standard deviation is 120. The sample mean was determined to be 320. What is the standard error?

15

Random samples of size 81 are taken from a process whose mean and standard deviation are 200 and 18, respectively. What is the standard error?

2

the following represents the probability distribution for the daily demand of microcomputers at a local store. demand: probability: 0. .1 1 .2 2 .3 3 .2 4 .2 What is the expected daily demand?

2.20

Using data in #11, what is the 50th percentile for time spent watching tv?

44

The amount of time that a sample of students spends watching tv per day is given below. student: time(minutes) 1 40 2 28 3 71 4 48 5 49 6 35 7. 40 8 57 What is the sample mean for the amount of time spent watching tv?

46

Using the data in #11, what is the 75th percentile for this sample data?

55

A researcher has collected the following sample data. 5. 12. 6. 8. 5 6. 7. 5. 12. 4 what is the median of this data?

6

A description of how the probabilities are distributed over the values the random variable can assume is called a probability distribution.

True

A probability distribution for all possible values of a sample statistic is known as a sampling distribution

True

A single numerical value used as an estimate of a population parameter is known as a point estimate.

True

A standard normal distribution is a normal distribution with a mean of 0 and a standard deviation of 1.

True

A subset of a population selected to represent the populations a sample.

True

After the data have been arranged from smallest value to largest value, the value in the middle is called the median.

True

The highest point of a normal curve occurs at the mean.

True

The interquartile range is the difference between the third and first quartiles.

True

The number of people in a waiting line is an example of quantitative variable.

True

The proportion of mailed-out questionnaires that were returned is an example of descriptive statistics.

True

The sum of the relative frequencies for all classes will always equal 1.

True

if A and B are mutually exclusive events with P(A) = .3 and P(B) = .5, then P(A n B) =. 0.

True

the complement rule states that the probability of an event not occurring is equal to 1 minus the probability of its occurrence.

True

A marketing manager instructs his team to make 80 telephone calls to attempt to sell an insurance policy. The random variable in this experiment is the number of sales made. This random variable is ___.

discrete random variable