An unconfined compression test was performed to determine the average strength of concrete cylinders (in psi). It is believed that the strength is approximately normally distributed with a standard deviation of 256 psi. A sample of 70 concrete cylinders was taken, and it was found that the average strength was 3000 psi. Find a 91% confidence interval for the true average strength of the concrete.

Be sure to:

• State the value for α.
• State whether you should use z or t and find the appropriate value. Round z-values to 2 decimals. Round t-values to 3 decimals.
• Find the confidence interval (to 2 decimals). State the parameter your confidence interval is for.
• Write a verbal interpretation of your confidence interval.

Answers

Answer 1

Answer:

Explained below.

Step-by-step explanation:

(1)

The confidence level is, 91%.

Compute the value of α as follows:

[tex]\text{Confidence level}\% =(100-\alpha \%)\\\\91% = 100-\alpha \%\\\\\alpha \%=100-91\%\\\\\alpha \%=9\%\\\\\alpha =0.09[/tex]

(2)

As the population standard deviation is provided, i.e. σ = 256 psi, the z value would be appropriate.

The z value for α = 0.09 is,

z = 1.69

(3)

Compute the 91% confidence interval as follows:

[tex]CI=\bar x\pm z_{\alpha/2}\cdot\frac{\sigma}{\sqrt{n}}[/tex]

     [tex]=3000\pm 1.69\cdot\frac{256}{\sqrt{70}}\\\\=3000\pm 51.71\\\\=(2942.29, 3057.71)[/tex]

(4)

The 91% confidence interval for population mean implies that there is a 0.91 probability that the true value of the mean is included in the interval, (2942.29, 3057.71) psi.


Related Questions

A car travels 180 miles in 3 hours, which is a rate of miles per hour.

Answers

Answer:

540

Step-by-step explanation:

multiply 180 by 3

Every 100 pounds on Earth are equivalent to 38 pounds on Mars.A boy weighs 60 pounds on Earth how much would he weigh on Mars

Answers

Answer:

22.8 pounds

Step-by-step explanation:

The answer is 22.8 because when you divide 100 by 38 you get 2.63157894737 and if you divide 60 by 2.63157894737 you get 22.8

Write an equation for the graph below which represents a logarithmic function f with base 2 or 3 translated and/or reflected. X=3 (7,1) (5,0) (4,-1)

Answers

Answer:

The answer is "[tex]\log(x-3)- \log(2)[/tex]"

Step-by-step explanation:

The asymptote is that when the group is 0 within. Let's all assume that log base 2 is: Log(ax-b); a position mostly online also they know. Let's use this (5,0)  and log(5a-b)=0; they get out of it 5a-b=1; now that the results for a and b must be known. So we can say unless the asymptote is x=3, 3a-b=0; then we have the equations system, and with a and b we can solve

[tex]\to b=5a-1 \\\\ \therefore\\\\\to 3a-(5a-1)=0\\\\\to 3a-5a+1=0\\\\\to -2a+1=0\\\\\to -2a=-1\\\\\to a=\frac{1}{2} \ and\ b= \frac{3}{2}[/tex]

[tex]\to \log(\frac{x}{2}-\frac{3}{2})\\\\\to \log(\frac{(x-3)}{2})\\\\\to \log(x-3)- \log(2)[/tex]

How do you do this question?

Answers

Answer:

y(0) = 3

Step-by-step explanation:

This is solved by plugging in each option one by one, and seeing which one results in a positive value for dy/dt.

dy/dt = (4 − 1) (1 − 2²) = -9

dy/dt = (7 − 1) (1 − 1²) = 0

dy/dt = (1 − 1) (1 − 2²) = 0

dy/dt = (-4 − 1) (1 − 0²) = -5

dy/dt = (3 − 1) (1 − 0²) = 2

Only the last option fits.

what is 656x106 rounded

Answers

Answer:

69536

LOLLLLLLLLLL

Answer:

69536

Step-by-step explanation: and rounded to the nearest what

Identify the type of slope each line has. Place your answer under each graph.

Answers

-3, 0, 1/2, undefined

if it is going down its negative if it goes up its positive

first one you can tell because each one to the right it goes 3 down

2nd is 0 because there is no slope to it, last one is undefined because it cant be all the numbers when x is -4

Question 3
The distribution of random variable R has mean 10 and standard deviation 4. The distribution of random variable S
has mean 7 and standard deviation 3. If Rand S are independent, what are the mean and standard deviation of the
distribution of R-S?
Mean 3 and standard deviation 1
B
Mean 3 and standard deviation 5
Mean 3 and standard deviation 7
mong
D
Mean 17 and standard deviation 1
E
Mean 17 and standard deviation 5

Answers

Answer:

(B) Mean 3 and standard deviation 5

Step-by-step explanation:

Property of mean

The mean of the sum or difference of two random variable R and S is the sum of their means.

μ (R-S) = μ(R) - μ(S)

μ(R-S) = 10 - 7 = 3

Property of standard deviation

The variance of Independent variable R and S is is the sum of their variances. Even when we subtract two random variables, we still add their variances; subtracting two variables increases the overall variability in the outcomes.

σ^2(R-S) = σ^2 (R) + σ^2(S)

            = 16 + 9           ( variance = (standard deviation)^2  )

             = 25

σ(R-S)  = 5

The mean of the  distribution of R-S is 3 and the standard deviation of the  distribution of R-S is 5 and this can be determined by using the given data.

Given :

The distribution of random variable R has a mean of 10 and a standard deviation of 4. The distribution of random variable S  has mean 7 and standard deviation 3.

The following steps can be used in order to determine the mean and standard deviation of the  distribution of R-S:

Step 1 - The mean can be determined by using the below formula.

[tex]\rm \mu(R-S) = \mu(R)-\mu(S)[/tex]

Step 2 - Substitute the values of [tex]\rm \mu(R)[/tex] and [tex]\rm \mu(S)[/tex] in the above expression.

[tex]\rm \mu(R-S) = 10-7[/tex]

[tex]\rm \mu(R-S) = 3[/tex]

Step 3 - The standard deviation can be determined by using the below formula.

[tex]\rm \sigma^2(R-S) = \sigma^2(R)+\sigma^2(S)[/tex]

Step 4 - Substitute the values of [tex]\rm \sigma(R)[/tex] and [tex]\rm \sigma(S)[/tex] in the above expression.

[tex]\rm \sigma^2(R-S) = 16+9[/tex]

[tex]\rm \sigma(R-S) = 5[/tex]

Therefore, the correct option is B).

For more information, refer to the link given below:

https://brainly.com/question/12402189

The revenue function is given by R(x)=x⋅p(x) dollars where x is the number of units sold and p(x) is the unit price. If p(x)=34(3)−x6, find the revenue if 6 units are sold. Round to two decimal places.

Answers

rawr jshsjsjsjshhsjsjsj

Mellssa will rent a car for the weekend. She can choose one of two plans. The first plan has an initial fee of $44 and costs an additional S0.14 per mile driven.
The second plan has an initial fee of $51 and costs an additional $0.09 per mile driven
For what amount of driving do the two plans cost the
Same?
mile
17
What is the cost when the two plans cost the same?
X
5
?

Answers

Answer:

Step-by-step explanation:

44+.14x = 51+.09x

.05x=7

140=x, or the amount of driving the two needs to do for the plans to be the same

44+14(.14)

plug it back in to find the cost

$63.60

Hii, can someone please help? I'm giving BRAINLIEST

Answers

Answer:

It would Be C I hoped this helped

The sum of three non-negative numbers is 36, and one of the numbers is twice one of the other numbers. What is the maximum value of the product of these three numbers?

Answers

Answer: 726.

Step-by-step explanation:

we have:

a, b and c non-negative numbers.

we know that:

a + b + c = 36.

(i also assume that the numbers are whole numbers)

and "one of the numbers is twice one of the others"

Then we can write:

a = 2*b

replacing that in the above equation, we get:

2*b + b + c = 36

3*b + c = 36.

Then the product between the 3 numbers will be:

P = a*b*c = (2*b)*b*c = 2*b^2*c.

Because we have b squared in the product, we want to find the maximum possible value of b, such that:

3*b + c = 36.

3*b = 36 - c

We know that 36 is a multiple of 3, and also is 3*b.

Then 36 - c must also be a multiple of 3, this means that c must be a multiple of 3 (and the smallest possible), which is 3.

Then if we have:

3*b = 36 - 3 = 33

3*b = 33

b = 33/3 = 11.

The prodct will be:

P = 2*(11^2)*3 = 726.

The maximum value of the product of the three given numbers is;

P_max  = 726

Let the three non-negative numbers be x, y and z

We are told that they sum up to 36.

Thus;

x + y + z = 36.

Now, one of the numbers is twice one of the other numbers.

Thus;

x = 2y

Then, we now have;

2y + y + z = 36

⇒ 3y + z = 36.

We want to find the maximum value of the  product between the 3 numbers. Let's say their product is P, then we have;

P = xyz

P = 2y²z

Since y is squared here, then let's make 3y the subject in 3y + z = 36.

3y + z = 36.

3y = 36 - z

since 3 is multiplied by y, it means that  36 - z be a multiple of 3 and we can infer that z must also be a multiple of 3. If we take z = 3, we have;

Then if we have:

3y = 36 - 3

3y = 33

y = 33/3

y = 11.

Since Product is P = 2y²z, then we have;

P = 2 × 11² × 3

P_max  = 726

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Solve for r. r + 62 ÷ 2 =1​

Answers

Hey there!

“r + 62 ÷ 2 = 1”

Combine your like terms

(62 ÷ 2)

62 ÷ 2 = 31

New equation

r + 31 = 1

SUBTRACT by 31

Like: r + 31 - 31 = 1 - 31

Cancel out: 31 - 31 because that gives you 0

Keep: 1 - 31 because that gives you the value of “r”

1 - 31 = -30

Therefore, your answer is: r = -30 ☑️

Good luck on your assignment and enjoy your day!

~LoveYourselfFirst:)

The different kinds of beads that Casey is
using to make purses come in packages of
3 and 9. What is the least number of each
kind of bead that Casey can buy to have an
equal number of each of the different kinds
of beads?

Answers

Answer:

Casey can buy 3 packages with 3 beads and one package with 9 beads to have the same number of beads of each kind.

Step-by-step explanation:

Given that:

The beads come in packages of 3 and 9.

To calculate the least number of beads that Casey can have, we will find the least common multiple of both packages.

Package of three = 3, 6, 9, 12, 15

Package of nine = 9, 18, 27, 36

The least common multiple of 3 and 9 is 9.

Hence,

Casey can buy 3 packages with 3 beads and one package with 9 beads to have the same number of beads of each kind.

I need it fasttttttt

5. Rex deposited $900 into an
account that earns 4% simple
interest. How many years will it
take for the value of the
account to reach $1,800?

Answers

Answer:

well, there is already $900 so 1800-900=900   now we need 4% of 900 which is $36   900 divided by 36 is 25

it will take 25 years

Step-by-step explanation:

plz mark brainliest i answered first

The number of years that will it take for the value of the account to reach $1,800 should be 25 years.

Calculation of the number of years:

Since the deposited amount is $900

The rate of interest is 4%

The future value is $1,800

So here the balance amount should be

= $1,800 - $900

= $900

Now 4% of $900 = 36

So the number of year should be

= [tex]900\div 36[/tex]

= 25 years

hence, The number of years that will it take for the value of the account to reach $1,800 should be 25 years.

Learn more about year here: https://brainly.com/question/16045495

Solve "43 -
O a = 3/5
O a = 3/4 .
O a = 4/3
O a = 5/3

Answers

Answer:

the answer to this question is 4/3

Answer:

C 4/3

Step-by-step explanation:

you're welcome <3

Find the simple interest paid to the nearest cent for each principal, interest rate, and time.

$2,620, 3%, 5 years

Pleaseee help!!!

Answers

Step-by-step explanation:

You deposit some money into a bank account paying 4% simple interest per year. You received $72 in interest after 3 years. How much the deposit (principal) was?

Hermina cut a 10 by 15 piece of cardboard down the diagonal


What is the c of the cut, in inches??

Answers

Answer:

[tex]\sqrt{325}[/tex]

Step-by-step explanation:

This is because you use Pythagorean theorem. a^2 + b^2 = c^2.

I’m so confused, please help

Answers

I think is D

PLEASE MARK ME AS BRAINLIEST

I like animals, what animals do you like?

Answers

Answer:

tigers

Step-by-step explanation:

Answer:

cats,bunnys,rabits,snakes,lizards,horses,dogs

Step-by-step explanation:

Lauren bought a television that cost $805. She plans to make equal payments of $38 each month until the television is paid in full. About how many payments will Lauren make?

Answers

the answer should be one year 10 months

Are the ratios 20:16 and 10:8 equivalent?​

Answers

No they are not equivalent

Helpppp ! Will give brainlist!

Answers

So it gives you the answer for the first one

1 and 5 for the first box because it says he visited 5 in his first month
Then it says he visited 2 more each following month meaning each time it’s going to go up 2

So the box should look like

1-5
2-7
3-9

Then we have to figure out what goes in the x when y equals 23
So you can just go up by each month until one reaches 23 and it will be 10

So the final part of the box should say

10-23


The amount of parks is proportional to the amount of months.

Answer:

5 parks

7 parks

9 parks

10 months

Step-by-step explanation:

1 month: 5 state parks

2 months:5+2=7 state parks

3 months:7+2=9 state parks

x months : 23 state parks

23-9 state parks = 14 state parks

14/2=7 it means 7 months more

3+7=10 months

10 months : 23 state parks

the smallest three digit whole number ending with 9 ​

Answers

Answer:

769

Step-by-step explanation:

Answer:

109

Step-by-step explanation:

Help plz:))) I’ll mark u brainliest
10 ez POINTS

Answers

I think is 24, 27, 2.
I hope is correct.

What does the point (0, 0) mean in this situation?

Answers

It’s undefined because division by zero is an undefined operation.

Answer:

at 0 hours, 0 miles were traveled

Anyone wanna help me with this‍‍

Answers

Question 1 Answer: both of them equal 20

Step-by-step explanation: when you add 9+3 it equals 12 then you add 8 and that makes 20. 9+8 also equals 17 then you add 3 which equals 20

An urn contains 17 white balls and 18 red balls. A sample of four balls is selected at random from the urn. What is the probability that the sample contains two white balls and two red ones?

a. 0.0286
b. 0.2286
c. 0.3974
d. 0.0944
e. 0.0442
f. None of the above.

Answers

Answer:

c. 0.3974

Step-by-step explanation:

Given;

number of white balls, W = 17

number of red balls, R = 18

Total number of balls, T = 35

The number of ways the event will occur is given by

= P(2 whites) and P(2 reds)

= P(2whites) x P(2 reds)

= 17C2 x 18C2

= 136 x 153

= 20,808

The total number of possible outcome

= 35C4

= 52,360

The probability = 20,808 / 52,360

                          = 0.3974

The correct option is "C"

Probability that the sample contains two white balls and two red ones is equal to 0.3974.

So, option c. is correct.

Permutations and combinations

Probability is a discipline of mathematics concerned with numerical explanations of the likelihood of an event occurring or the truth of a claim.

Number of white balls [tex]=\boldsymbol{17}[/tex]

Number of red balls [tex]=\boldsymbol{18}[/tex]

Total number of balls [tex]=\boldsymbol{35}[/tex]

Probability that the sample contains two white balls and two red ones  

[tex]=\frac{\binom{17}{2}\binom{18}{2}}{\binom{35}{4}}[/tex]

[tex]=\frac{\frac{17!}{15!2!}\frac{18!}{16!2!}}{\binom{35!}{31!4!}}[/tex]

[tex]=\boldsymbol{0.3974}[/tex]

So, option c. is correct.

Find more information about combinations here:

https://brainly.com/question/815369?referrer=searchResults

A football team has a total of 800 jerseys. There are 6 medium size jerseys. What is the percentage of medium size jerseys?

Answers

0.75% is the answer to this question

If you want to buy an item in a store that costs $9 and is on sale for 20% off, then how much would the item actually cost you after the discount? Round to the nearest cent.

Answers

Answer:

Step-by-step explanation:

20% off is $1.80

9-1.8

the cost would be $7.20

If a function is defined by the formula y = 1/2 x + 3 and its domain is given by the set { -4,0,8}, then which set gives the functions range

Answers

Answer:

(-4, 8)

Step-by-step explanation:

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