1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Stels [109]
3 years ago
10

Let X1, X2, and X3 represent the times necessary to perform three successive repair tasks at a service facility. Suppose they ar

e normal random variables with means of 50 minutes, 60 minutes, and 40 minutes, respectively. The standard deviations are 15 minutes, 20 minutes, and 10 minutes, respectively. a Suppose X1, X2, and X3 are independent. All three repairs must be completed on a given object. What is the mean and variance of the total repair time for this object.
Mathematics
1 answer:
belka [17]3 years ago
8 0

Answer:

The mean of the total repair time is 150 minutes.

The variance of the total repair time is 725 minutes^2.

Step-by-step explanation:

To solve this problem, we have to use the properties of the mean and the variance. Our random variable is the sum of 3 normal variables.

In the case, for the mean, we have that the mean of the sum of 3 normal variables is equal to the sum of the mean of the 3 variables:

y=x_1+x_2+x_3 \\\\E(y)=E(x_1+x_2+x_3)=E(x_1)+E(x_2)+E(x_3)\\\\E(y)=50+60+40=150

For the variance, we apply the property for the sum of independent variables (the correlation between the variables is 0):

V(y)=V(x_1)+V(x_2)+V(x_3)\\\\V(y)=s_1^2+s_2^2+s_3^2\\\\V(y)=15^2+20^2+10^2\\\\V(y)=225+400+100\\\\V(y)=725

You might be interested in
Plz help me it worth 50% of my grade tell wethere it’s proportional of not
Julli [10]

Answer:

2) is not proportional, 3) is not proportional, 5) is proportional, 6) is not proportional.

Step-by-step explanation:

Number 2 is not proportional since it doesn't go through the origin on the graph and the line is not a straight line.

Number 3 does not go through the origin, so number 3 is also not proportional.

Number 5 is proportional since when you divide y by x, it is always 7.

Number 6 is not proportional because when you divide y by x or x by y there are not the same answers.

5 0
2 years ago
Can you ever use a calculator to determine if a number is rational or irrational?explain.
AysviL [449]
Yes, for fractions you can multiply the denominator by the numerator. For square roots you can use the square root button.
8 0
3 years ago
Read 2 more answers
If the ratio of men to women is 3:2 and there are 120 men, how many women would there be?
zavuch27 [327]
There would be 80 women.
Here's the work:
120 divided by 3 = 40 
If the ratio is 3:2, there is always one less woman then men, so you subtract the 40 men in a group and you get your answer of 80

Hope I helped!! :)
5 0
2 years ago
Read 2 more answers
Martina read that approximately 10% of all people are left-handed. She wants to design a simulation to approximate the probabili
marta [7]

Answer:

20

Step-by-step explanation:

8 0
3 years ago
Read 2 more answers
How does writing an equation help you solve a problem?
vredina [299]
So you wont forget what you wrote and it helps you to figure out the problem. I hope this helps.
8 0
3 years ago
Other questions:
  • What are the two types of compound inequalities? Give an example of each?
    10·2 answers
  • Four out of 5 dentists recommend Sparkle toothpaste. What percent of dentists recommend sparkle toothpaste?
    10·2 answers
  • How can linear equations and functions be written and graphed? Explain how shifting the graph changes the function.
    13·1 answer
  • What is the average rate of change of f(x), represented by the table of values, over the interval [-3, 2]?
    6·2 answers
  • 9
    12·1 answer
  • Mark can buy 15 tea bags for $3. What is the unit rate of price per bag? At that rate, how many tea
    9·2 answers
  • Help im on a meeting this need to be done
    10·1 answer
  • Select the correct answer.
    10·2 answers
  • 3(2x+4)=−36<br><br> Find the variable
    13·2 answers
  • In the number 7,777. 777, what is the difference between the 7 in the hundreds place and the 7 in the column to its left?.
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!