Question 1

What is the probability that x is less than 5, given the function below? f(x) = (1/10) e-x/10 x  0

Accepted Answer

A)  0.6065 
B)  0.0606 
C)  0.3935 
D)  0.9393

Question 2

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. What is the minimum weight of the middle 95% of the players?

Accepted Answer

A)  196 
B)  151 
C)  249 
D)  190

Question 3

A professor at a local university noted that the exam grades of her students were normally distributed with a mean of 73 and a standard deviation of 11. The professor has informed us that 8.75 percent of her students received grades of A. What is the minimum score needed to receive a grade of A?

Accepted Answer

A)  85.00 
B)  95.00 
C)  87.92 
D)  90.00

Question 4

The center of a normal curve

Accepted Answer

A)  is always equal to zero. 
B)  is the mean of the distribution. 
C)  cannot be negative. 
D)  is the standard deviation.

Question 5

The z score for the standard normal distribution

Accepted Answer

A)  is always equal to zero. 
B)  can never be negative. 
C)  can be either negative or positive. 
D)  is always equal to the mean.

Question 6

z is a standard normal random variable. The P(1.5 < z < 2.3) equals

Accepted Answer

A)  0.9439. 
B)  0.0561. 
C)  0.9225. 
D)  0.0775.

Question 7

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 percentage of tires will have a life of 35,000 to 45,000 miles?

Accepted Answer

A)  31.73% 
B)  68.27% 
C)  50% 
D)  95%

Question 8

The travel time for a college student traveling between her home and her college is uniformly distributed between 40 and 90 minutes. The probability that she will finish her trip in 60 minutes or less is

Accepted Answer

A)  0.8. 
B)  0.4. 
C)  0.2. 
D)  1.00.

Question 9

Use the normal approximation to the binomial distribution to answer this question. Eleven percent of all students at a large university are absent on Mondays. If a random sample of 12 names is called on a Monday, what is the probability that four students are absent?

Accepted Answer

A)  0.0285 
B)  0.9935 
C)  0.0065 
D)  0.9715

Question 10

The weight of football players is normally distributed with a mean of 200 pounds and a standard deviation of 25 pounds. What percent of players weigh between 175 and 225 pounds?

Accepted Answer

A)  50% 
B)  68.27% 
C)  31.73% 
D)  95%

Question 11

For a uniform probability density function, the height of the function

Accepted Answer

A)  cannot be larger than one. 
B)  is the same for each value of x. 
C)  is different for various values of x. 
D)  decreases as x increases.

Question 12

In a standard normal distribution, the range of values of z is from

Accepted Answer

A)  minus infinity to infinity. 
B)  -1 to 1. 
C)  0 to 1. 
D)  -3.09 to 3.09.

Question 13

The standard deviation of a normal distribution

Accepted Answer

A)  is always 0. 
B)  is always 1. 
C)  can be any value. 
D)  cannot be negative.

Question 14

Given that z is a standard normal random variable, what is the value of z if the area to the right of z is 0.9634?

Accepted Answer

A)  1.79 
B)  -1.79 
C)  0.79 
D)  -0.79

Question 15

The assembly time for a product is uniformly distributed between 2 to 10 minutes. What is the value of probability density function in the interval between 2 and 10?

Accepted Answer

A)  0.25 
B)  0.125 
C)  8.00 
D)  0.00

Question 16

x is a normally distributed random variable with a mean of 7 and a standard deviation of 2. The probability that x is between 6.48 and 7.56 is

Accepted Answer

A)  0.9524. 
B)  0.0476. 
C)  0.7872. 
D)  0.2128.

Question 17

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 percentage of MBA's will have starting salaries of $34,000 to $46,000?

Accepted Answer

A)  38.49% 
B)  38.59% 
C)  50% 
D)  76.98%

Question 18

For a continuous random variable x, the height of the function at x is

Accepted Answer

A)  the probability at a given value of x. 
B)  0.50, since it is the middle value. 
C)  a value less than zero. 
D)  named the probability density function f(x).

Question 19

x is a normally distributed random variable with a mean of 6 and a variance of 4. The probability that x is greater than 8.75 is

Accepted Answer

A)  0.9154. 
B)  0.0846. 
C)  0.0775. 
D)  0.9225.

Question 20

z is a standard normal random variable. What is the value of z if the area between -z and z is 0.754?

Accepted Answer

A)  0.377 
B)  0.123 
C)  2.16 
D)  1.16

Exam 6: Continuous Probability Distributions

What is the probability that x is less than 5, given the function below? f(x) = (1/10) e^-^x^/10 x 0