Answer:
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the lifetime for a TV of a population, and for this case we know the distribution for X is given by:
Where 
and 
We are interested on this probability
And the best way to solve this problem is using the normal standard distribution and the z score given by:
If we apply this formula to our probability we got this:
And we can find this probability like this:
And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.
Y=6 In this equation you also use combine like terms .
Answer:
B, Work with the math instructors to create a list of students currently taking a math class. Randomly select
Step-by-step explanation:
Let's think of each scenario at a time.
(A) We select 100 students enrolled in college randomly that should be fine because we are taking only students that can take classes. this rules out faculty members and any other persons but also there may be students that will never take any math course as part of their study plan, this is ruled out on that basis.
(B)if we take 100 students from the list of math instructor, that will ensure that we have taken students that are taking math class now, and math is part of their study plan, seems fine.
(C) visiting cafeteria randomly on multiple days will give us random persons that may not even be enrolled in university. this can be ruled out on that basis.
(D)Ten class at random and surveying each student in every class will make sampling size large or small depending on students enrolled in each of the class this will not give us reliable results.
We can conclude that (B) is the beast method for obtaining reliable results.
I think your answer is gonna be 20
