The lifetimes of a certain brand of light bulbs are known to be normally dsitributed with a mean of 1700 hours and standard deviation of 400 hours. A random sample of 64 of these light bulbs is taken. The probability is 0.20 that the sample mean lifetime is more than how many hours?
A. 1652.
B. 1725.
C. 1752.
D. 1670.

Answers

Answer 1

Answer:

1742 hours

Step-by-step explanation:

To solve this question, we need to understand the normal probability distribution and the central limit theorem.

Normal probability distribution

When the distribution is normal, we use the z-score formula.

In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.

Central Limit Theorem

The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean [tex]\mu[/tex] and standard deviation [tex]s = \frac{\sigma}{\sqrt{n}}[/tex].

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

Single light:

Mean of 1700 hours and standard deviation of 400 hours, which means that [tex]\mu = 1700, \sigma = 400[/tex]

Sample of 64:

This means that [tex]n = 64, s = \frac{400}{\sqrt{64}} = 50[/tex]

The probability is 0.20 that the sample mean lifetime is more than how many hours?

This is the 100 - 20 = 80th percentile, which is X when Z has a pvalue of 0.8. So X when Z = 0.84

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

By the Central Limit Theorem

[tex]Z = \frac{X - \mu}{s}[/tex]

[tex]0.84 = \frac{X - 1700}{50}[/tex]

[tex]X - 1700 = 50*0.84[/tex]

[tex]X = 1700 + 50*0.84[/tex]

[tex]X = 1742[/tex]


Related Questions

random khan question and I haven't done this in a year, I'm struggling.

Answers

Answer:

Add maybe

Step-by-step explanation:

add the 500+400+200 try that hope it helps have a great day

Jason planted 11 packs of seed in his 4 gardens. he Planted the same amount of seed in each garden. how many packs of Seed Were planted in each were planted in each garden?

Answers

2.75 packs

Step-by-step explanation:

11 packs ÷4 gardens =2.75 packs per garden

The bigger

the number the more

factor pairs it has.

Use examples to show that Dexter is wrong.

Answers

Answer:

See Explanation

Step-by-step explanation:

Required

Prove that Dexter is wrong

To prove that Dexter is wrong, we use the following numbers.

[tex]Number = 4[/tex]

The factors are:

[tex]Factor = 1,2\ and\ 4[/tex]

3 factors

Using a greater number:

[tex]Number = 5[/tex]

The factors are:

[tex]Factor = 1\ and\ 5[/tex]

2 factors

From the above analysis:

4 has 3 factors and 5 has 2 factors; which shows that 5 has fewer factors

This shows that Dexter is wrong

Security A rounds every 2 minutes and 20 seconds in the gate 1. Security B rounds every 1 minute and 40 seconds in the gate 2. If they conduct rounds at the same time. After how many minutes they will rounds together again?

Answers

Answer:

[tex]Time = 11\frac{2}{3}\ min[/tex]

Step-by-step explanation:

Given

[tex]Security\ A = 2\ mins, 20\ secs[/tex]

[tex]Security\ B = 1\ mins, 40\ secs[/tex]

Required

After how many minutes, will they round together

First, convert the given time to minutes

[tex]Security\ A = 2\ mins, 20\ secs[/tex]

[tex]Security\ A = 2\ mins+ 20\ secs[/tex]

[tex]Security\ A = 2\ mins+ \frac{20}{60}\ min[/tex]

[tex]Security\ A = 2\ mins+ \frac{1}{3}\ min[/tex]

[tex]Security\ A = 2\frac{1}{3}\ min[/tex]

[tex]Security\ B = 1\ mins, 40\ secs[/tex]

[tex]Security\ B = 1\ mins+ 40\ secs[/tex]

[tex]Security\ B = 1\ mins+ \frac{40}{60}\ min[/tex]

[tex]Security\ B = 1\frac{2}{3}\ min[/tex]

So, we have:

[tex]Security\ A = 2\frac{1}{3}\ min[/tex]

[tex]Security\ B = 1\frac{2}{3}\ min[/tex]

List out the multiples of the time of both security personnel take round.

[tex]Security\ A = 2\frac{1}{3}min,\ 4\frac{2}{3}min,\ 7min,\ 9\frac{1}{3}min,\ 11\frac{2}{3}min...[/tex]

[tex]Security\ B = 1\frac{2}{3}min,\ 3\frac{1}{3}min,\ 5min,\ 6\frac{2}{3}min,\ 8\frac{1}{3}min,\ 10min\ ,11\frac{2}{3}min,...[/tex]

In the above lists, the common time is:

[tex]Time = 11\frac{2}{3}\ min[/tex]

This implies that they go on round after [tex]11\frac{2}{3}\ min[/tex]

A store manager combines trail mix that is 30% raisins with a trail mix that is 55% raisins. He makes 800 lbs of trail mix that is 40% raisins. How many pounds of each trail mix does the manager use?

Answers

Answer:

320 pounds of 55% raisins trail mix

480 pounds of 30% raisins trail mix

Step-by-step explanation:

i did it on RSM and got it right

Elena mixes 5 cups of apple juice with with 2 cups of ginger ale to make punch for a party she wants to make 35 cups of punch how much apple juice does she need to buy?​

Answers

Answer:

25 cups of apple juice and 10 cups of sparking water.

Step-by-step explanation:

Let f be the function given by f(x) = x +
Vx+1
X - 1
Find and simplify f(5).

Answers

Answer:

A)4

Step-by-step explanation:

Since (3+1)^1/2=2

and 3-1=2

2/2=1

3+1=4

A submarine was situated 832 feet below sea level. If it descends 289 feet, what is its new position?

Answers

It's new position is 1121 feet below sea level.

(In this problem u are descending into a negative value so it made sense for me to add for some reason).

Hope this helps and have a good day.

Also, as proof I included my calculator showing the logic behind it. Sorry for bad Camera quality.

-R3TR0 Z3R0

Need help on only 27 please need ASAP thanks

Answers

Answer:

8 is not in the solution set

Step-by-step explanation:

Given, -y + 7 < -4

To find out if 8 is in the solution set, substitute y = 8 in the inequality and solve to see if the statement would be true.

Thus:

-8 + 7 < -4

-1 < -4

This -1 is less than -4. This is actually not TRUE. -1 is rather greater than -4.

Therefore, 8 is not in the solution set.

zach read a book10 min every weekend for the first month 20min in 2nd month 40 min in third month and 80 min in 4th month
victoria read a book 35 everyweekend for first month 50 min second month 65 min third month 80 min 4 the month which method is used linear or exponential

Answers

Answer:

Zach time of reading every weekend forms a sequence with these terms: 10, 20, 40, 80. On the other hand, that of Victoria forms a sequence with terms: 35, 50, 65, 80. By keenly observing the sequences, Zach's sequence is a geometric sequence with a common ratio equal to 2 and Victoria's sequence is an arithmetic or linear sequence with a common difference of 15. Thus, the answer is letter B.

Step-by-step explanation:

Malcolm buys a 5/6-pound bag of black beans and a 3/4-pound bag of pinto

Answers

Answer:

1 7/12

Step-by-step explanation:

I think that you want to know how many total pounds of beans do you have.

Well, to find this, simply find the LCM of 6 and 4. That is 12.

So convert the fractions to have a denominator of 12.

10/12, 9/12

Now add:

(10+9)/12 = 19/12 = 1 7/12


solve each equation for given variable
- 12 = 6i- 6

Answers

Answer: i = -1

Explanation:
First get the variable by itself. To do that, add six to both sides of the equation. You will have -6 = 6i. Than divide both sides by 6. It will give you i = -1.
-12 = 6i - 6
-12 + 6 = 6i - 6 + 6
-12 + 6 = 6i
(-12 + 6)/6 = (6i)/6
(-12 + 6)/6 = i

i = (-12 + 6)/6

Which statement describes the graph

Answers

Answer:

Your answer is A

Step-by-step explanation:

I hope I helped :)

Your answer is going to be A.

Write an integer for deposit of $100

Answers

Write an integer for deposit of $100:

-$100

PLEASE HELP !!! ILL GIVE BRAINLIEST!! *DONT SKIP* ILL GIVE 40 POINTS.

Answers

Answer:

5.5

Step-by-step explanation:

The answer is 5.5 to you answer.hope it helps

Please help me?! I don’t have a lot of time? Please I will give brainiest for the correct answer !

Answers

Answer:

It should be -3

Hope it helped i tried to help you ASAP

Step-by-step explanation:

what is the answer
y-11=25-3y

Answers

Answer:

9

Step-by-step explanation:

y-11=25-3y

y + 3y = 25 + 11

4y = 36

y = 36 / 4

y = 9

Hope it will help :)

Pls help 20 points this question is for my friend

Answers

Answer:

750 cubic feet

Step-by-step explanation:

The Wall Street Journal reported that the median salary for middle-level manager jobs was approximately $85,000 (The Wall Street Journal, August 6, 2013). Suppose that an independent study of middle-level managers employed at companies located in Atlanta, Georgia, was conducted to compare the salaries of managers working at firms in Atlanta to the national average. The following data show the salary, in thousands of dollars, for a 8. sample of 15 middle-level managers.
108 83 106 73 53 85 80 63 67 75 124 55 93 118 77
a. Compute the median salary for the sample of 15 middle-level managers. How does the median for this group compare to the median reported by The Wall Street Journal?
b. Compute the mean annual salary and discuss how and why it differs from the median a. b. computed in part (a).
c. Compute the first and third quartiles.

Answers

Answer:

Median = $80,000 ; Mean = $84,000 ; Q1 = 67,000 ; Q3 = 106,000

Step-by-step explanation:

Given the data :

108 83 106 73 53 85 80 63 67 75 124 55 93 118 77

Reorderd data :

53, 55, 63, 67, 73, 75, 77, 80, 83, 85, 93, 106, 108, 118, 124

The median salary:

1/2(n+1)th term

Sample size, n = 15

1/2 (15 + 1)th term

1/2(16)th term

8th term = 80

Median is $80,000

Median reported by Wall Street Journal approximately $85000

The obtained and reported values are close

The mean annual salary :

ΣX / n = 1260 / 15 = 84

Mean annual salary = $84,000

Mean is the average of all earnings combined, median is the mid value of he data.

First and third quartile :

Q1 = 1/4(n+1)th term

Q1 = 1/4(16)th term

Q1 = 4th term = 67

Third quartile:.

Q3 = 3/4(n+1)th term

Q3 = 3/4(16)th term

Q3 = 12th term = 106

By eating 1 egg, 1 cupcake, and 1 slice of pizza, a child consumes 300 mg of cholesterol. If the child eats 3 cupcakes and 4 slices of pizza, he or she takes in 86 mg of cholesterol. By eating 2 eggs and 1 cupcake, a child consumes 566 mg of cholesterol. How much cholesterol is in each item?

Answers

Answer:

cholesterol in egg= 273 mg

cholesterol in cupcake = 18 mg

cholesterol in slice of pizza = 9 mg

Step-by-step explanation:

Given data:

1 egg , 1 cupcake , 1 slice of pizza  = 300mg

3 cupcakes , 4 slices of pizza = 90mg

2 eggs , 1 cupcake = 564mg

Let egg be x , let cupcake be y and let pizza be y

x + y + z = 300 (equation 1)

0x + 3y + 4z = 90 (equation 2)

2x + y + 0z = 564 (equation 3)

Using equation 1 and equation 2

x + y + z = 300 (Multiply equation by 3)

0x + 3y + 4z = 90

3x + 3y +3z =900

0x +3y +4z = 90  (Subtracting the equations)

3x - z = 810  (equation 4)

Using equation 2 and equation 3

0x + 3y + 4z = 90

2x + y + 0z = 564 (Multiply equation by 3)

0x + 3y + 4z = 90

6x +3y + 0z = 1692 (Subtracting the equations)

-6x +4z =-1602  (equation 5)

Solving equation 4 and equation 5

3x - z = 810  therefore z =3x -810

Substituting z into equation 5

-6x +4(3x - 810) =-1602  

-6x + 12x - 3240 = -1602

6x = -1602+3240

6x = 1638

x = 273

Substituting x into z = 3x - 810

z = 3(273) - 810

z = 819-810

z = 9

Using equation 1 to find y

x + y + z = 300

273 + y + 9 = 300

282 + y = 300

y = 300-282

y = 18

What is the volume of the rectangular prism?​

Answers

Answer:

15 0/0

Step-by-step explanation:

15 cubes on each side which totals to 30 cubes. To get the volume 15 cm multiply 30 x 1/2 = 15 the amount of volume

Answer:

15[tex]cm^{3}[/tex]

Step-by-step explanation:

ok...each of those boxes are 1/2 cm

What is the easiest thing to do is to count the front of the rectangular prism and there are 15 cubes. Now double it, and you get 30 cubes, now since each cube is 1/2 or 0.5, we get can do 0.5 x 30 and we get 15

Hope this helped!

Have a supercalifragilisticexpialidocious day!

What is 13x + 21y - 14x - y simplified?

Answers

Answer:

-x + 20y

Step-by-step explanation:

trust me.. its right

1. Maya had a dozen white eggs
and a dozen brown eggs in her
refrigerator. She used 6 white
eggs and 8 brown eggs to make
breakfast. How many eggs does
she have left?

Answers

Answer:

6 white & 4 brown

Step-by-step explanation:

12-6=6

12-8=4

!! PLEASE HELP, TIMED!!Multiple choice, BRAINLIEST for correct answer!

Answers

Answer:

I'm not going to lie I'm not 100% sure but I think it's c

Answer:

D

Step-by-step explanation:

4x=4+2y

3y=5+2x

Help person right gets brainlist​

Answers

correct answer is = 3 17/28
brainliest?
P= 3 17/28
If its mixed number

P=3.60714285
If its need to be decimal

Just copy the answer from the pic

Plz help me! I’m not sure how to do these!

Answers

Step-by-step explanation:

2. x =101

3. x= 120

4. x= 30

I am very confused in question no 1 and 5 th .

hope this will be helpful to you.

plz mark my answer as brainlist if you find it useful .

The equation S = 50 + 45w represents the savings, S, after w weeks working and
depositing (putting in) money into a savings account at the bank.
Determine whether there is a proportional relationship between S and w.
Explain your reasoning.

Answers

Answer:

yes

Step-by-step explanation:

50 can be the initial money in the account and she can be depositing 45 dollars every (w) weeks and it will show her (S) savings

Suppose that c is a number for which the equation c÷c = 1 is false. What is c?

Answers

Answer:

Hope it help

Mark me as brainliest

Step-by-step explanation:

.3x+.65 x 175=.50(x+175)
Can you please explain this step by step? Kinda confused about how to figure it out.

Answers

Answer:

[tex]x=131.25[/tex]

Step-by-step explanation:

[tex]0.3x+0.65*175=0.5(x+175)[/tex]

[tex]0.3x+113.75=0.5x+87.5[/tex] (Simplify both sides of the equation by multiplying on the LHS and distributing on the RHS)

[tex]0.3x+113.75-0.5x=0.5x+87.5-0.5x[/tex] (Subtract [tex]0.5x[/tex] from both sides of the equation to get all [tex]x[/tex] terms to one side)

[tex]-0.2x+113.75=87.5[/tex] (Simplify)

[tex]-0.2x+113.75-113.75=87.5-113.75[/tex] (Subtract [tex]113.75[/tex] from both sides of the equation to isolate [tex]x[/tex])

[tex]-0.2x=-26.25[/tex] (Simplify)

[tex]\frac{-0.2x}{-0.2} =\frac{-26.25}{-0.2}[/tex] (Divide both sides of the equation by [tex]-0.2[/tex] to get rid of [tex]x[/tex]'s coefficient)

[tex]x=131.25[/tex] (Simplify)

Hope this helps!

Write an equation of the parabola with focus (0, 10) and vertex at the origin

Answers

Answer:

f(x) = (1/10)x²

Step-by-step explanation:

This is the answer that  I think it is but I am not sure if it is right...

Hope this helps!

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