Question 1

After arriving at the university student medical clinic, the waiting times to receive service after checking-in follow an exponential distribution with a mean of 10 minutes. Calculate the probability a student waits between 8 and 12 minutes.

Accepted Answer

The answer of After arriving at the university student medical...

Question 2

A study conducted by a local tennis center revealed that 25 percent of its new members have novice level tennis skills. A membership drive in a metropolitan area resulted in 500 new members. What is the probability that 110 or less of the new members are novice tennis players?

Accepted Answer

The answer of A study conducted by a local tennis...

Question 3

The formula to convert any normal distribution for a random variable, x, to the standard normal distribution is ____________.

Accepted Answer

The answer of The formula to convert any normal distribution...

Question 4

The exponential distribution can be used to predict ________.

Accepted Answer

The answer of The exponential distribution can be used to...

Question 5

The center of a normal probability distribution is ________.

Accepted Answer

A)  the same as the standard deviation or the distribution 
B)  never negative 
C)  the mean of the distribution 
D)  always equal to zero

Question 6

A binomial distribution has 100 trials (n = 100) with a probability of success of 0.25 (π = 0.25). We would like to find the probability of 75 or more successes using the normal distribution to approximate the binomial. Applying the continuity correction factor, what value would be used to calculate a z-score?

Accepted Answer

A)  74.5 
B)  75 
C)  75.5 
D)  25

Question 7

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution, what test score separates the top 25% of the students from the lower 75% of students?

Accepted Answer

A)  70.00 
B)  74.69 
C)  65.31 
D)  75.25

Question 8

The average starting salary of individuals with a master's degree in statistics is normally distributed with a mean of $48,000 and a standard deviation of $6,000. What is the probability that a randomly selected individual with a master's in statistics will get a starting salary of at least $55,500?

Accepted Answer

A)  0.121 
B)  0.891 
C)  0.379 
D)  0.098

Question 9

The shape of any uniform probability distribution is ____________.

Accepted Answer

A)  Negatively skewed 
B)  Positively skewed 
C)  Rectangular 
D)  Bell-shaped

Question 10

An accelerated life test on a large number of type-D alkaline batteries revealed that the mean life for a particular use before they failed is 19.0 hours. The distribution of the lives approximated a normal distribution. The standard deviation of the distribution was 1.2 hours. About 95.44% of the batteries failed between what two values?

Accepted Answer

A)  8.9 and 18.9 
B)  12.2 and 14.2 
C)  14.1 and 22.1 
D)  16.6 and 21.4

Question 11

Consider a continuous random variable x, which is uniformly distributed between 65 and 85. The probability of x taking on a value between 75 to 90 is ________.

Accepted Answer

A)  0.75 
B)  1.00 
C)  0.50 
D)  0.075

Question 12

The mean of a normal probability distribution is 500 and the standard deviation is 10. About 95% of the observations lie between what two values?

Accepted Answer

A)  475 and 525 
B)  480 and 520 
C)  400 and 600 
D)  350 and 650

Question 13

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

Accepted Answer

A) True 
 B)False

Question 14

The average score of 100 students taking a statistics final was 70 with a standard deviation of 7. Assuming a normal distribution, what is the probability that a student scored greater than 65?

Accepted Answer

A)  0.2611 
B)  0.2389 
C)  0.7611 
D)  -0.714

Question 15

A normally distributed random variable has _________.

Accepted Answer

A)  Any value between -∞ and + ∞. 
B)  Discrete values. 
C)  Any value between specified minimum and maximum values. 
D)  Only two values, success and failure.

Question 16

The employees of Cartwright Manufacturing are awarded efficiency ratings. The distribution of the ratings approximates a normal distribution. The mean is 400, the standard deviation is 50. What is the area under the normal curve between 400 and 482?

Accepted Answer

A)  0.5000 
B)  0.4495 
C)  0.3413 
D)  0.4750

Question 17

To apply the normal approximation to a binomial distribution, what must be true?

Accepted Answer

The answer of To apply the normal approximation to a...

Question 18

For a normal distribution, what is the likelihood (expressed as a percentage) that a random variable is within plus and minus two standard deviations of the mean?

Accepted Answer

A)  68.26% 
B)  99.74% 
C)  34.13% 
D)  95.44%

Question 19

The upper and lower limits of a uniform probability distribution are __________.

Accepted Answer

A)  Positive and negative infinity 
B)  Plus and minus three standard deviations 
C)  0 and 1 
D)  The maximum and minimum values of the random variable

Question 20

A study conducted by a local tennis center revealed that 25 percent of its new members have novice level tennis skills. A membership drive in a metropolitan area resulted in 500 new members. What is the probability that between 110 and 130 of the new members are novice tennis players?

Accepted Answer