Random_Variables_Checkpoint_3 pdf

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Module Random Variables 
Random Variables Checkpoint 3 
Step 1 of 1 
These three questions refer to the following information: 
Color-blindness is any abnormality of the color vision system that causes a person to see colors 
differently than most people, or to have difficulty distinguishing among certain colors 
(www.visionrx.com). 
Color-blindness is gender-based, with the majority of sufferers being males. 
Roughly 8% of white males have some form of colorblindness, while the incidence among white 
females is only 1%. 
A random sample of 20 white males and 40 white females was chosen. 
Let X be the number of males (out of the 20) who are color-blind. 
Let Y be the number of females (out of the 40) who are color-blind. 
Let Z be the total number of color-blind individuals in the sample (males and females together). 
Question 1 of 3 Points: 0 out of 10 
Which of the following is true about the random variables X, Y, and Z? 
 X is binomial with n = 20 and p = .08. 
 Y is binomial with n = 40 and p = .01. 
 Z is not binomial. 
 All of the above are true. 
 Only (A) and (B) are true. 
This is not quite right. Although this statement is true, there is a better option available. Consider 
the remaining options. (D) is the right answer. 
Question 2 of 3 Points: 10 out of 10 
What is the probability that exactly 2 of the 20 males are color-blind? (Note: Some answers are 
rounded.) 
 .08 
 .2711 
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 .0143 
 .5422 
 .0159 
Good job! We need to find P(X = 2) where X is binomial with n = 20 and p = 0.08. 
 
Question 3 of 3 Points: 10 out of 10 
What is the mean and standard deviation of the random variable Y (the number of females out of 
40 who are color blind)? Answers may be rounded. 
mean= 40, standard deviation=.01 
mean =.01, standard deviation = 40 
mean =0.4, standard deviation = .629 
mean = 0.4, standard deviation = .396 
We cannot find the mean and standard deviation since the probability distribution table is not 
given. 
Good job! Indeed the mean and standard deviation of a binomial random variable are np and 
 
respectively. In this case 
 
and 
 
 
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