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muminat
3 years ago
7

Provide an appropriate response. In order to efficiently bid on a contract, a contractor wants to be 95% confident that his erro

r is less than two hours in estimating the average time it takes to install tile flooring. Previous contracts indicate that the standard deviation is 4.5 hours. How large a sample must be selected?
a.19
b.4
c.5
d.20
Mathematics
1 answer:
lidiya [134]3 years ago
5 0

Answer:

d. 20

Step-by-step explanation:

Standard deviation is 4.5

Margin error for the problem is 2 hours

Probability 95%, that means that the siginficance level α is 1 – p

α = 1 – 0.95 = 0.05

margin of error (ME) can be defined as follows

ME = Z(α/2) * standard deviation/ √n

Where n is the sample size

Z(0.05/2) = Z(0.025)

Using a z table Z = 1.96

Now, replacing in the equation and find n

2 = 1.96 * 4.5/ √n

2 = 8.82/√n

√n = 8.82/2

√n = 4.41

n = 4.41^2

n = 19.44 ≈ 20

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Historically, the mean yield of corn in the United States has been 120 bushels per acre with a standard deviation of 12. A surve
Illusion [34]

Answer:

z=\frac{125-120}{\frac{12}{\sqrt{40}}}=2.64    

P-value

Since is a two sided test the p value would be:  

p_v =2*P(z>2.64)=0.0082  

And the best answer would be

B 0.0082

Step-by-step explanation:

Data given and notation  

\bar X=125 represent the mean height for the sample  

\sigma=12 represent the population standard deviation

n=40 sample size  

\mu_o =120 represent the value that we want to test

\alpha represent the significance level for the hypothesis test.  

t would represent the statistic (variable of interest)  

p_v represent the p value for the test (variable of interest)  

State the null and alternative hypotheses.  

We need to conduct a hypothesis in order to check if the true mean is 120 or not, the system of hypothesis would be:  

Null hypothesis:\mu = 120  

Alternative hypothesis:\mu \neq 120  

If we analyze the size for the sample is > 30 and we know the population deviation so is better apply a z test to compare the actual mean to the reference value, and the statistic is given by:  

z=\frac{\bar X-\mu_o}{\frac{\sigma}{\sqrt{n}}}  (1)  

z-test: "Is used to compare group means. Is one of the most common tests and is used to determine if the mean is (higher, less or not equal) to an specified value".  

Calculate the statistic

We can replace in formula (1) the info given like this:  

z=\frac{125-120}{\frac{12}{\sqrt{40}}}=2.64    

P-value

Since is a two sided test the p value would be:  

p_v =2*P(z>2.64)=0.0082  

And the best answer would be

B 0.0082

4 0
3 years ago
Steps to scientific notation
chubhunter [2.5K]
1.Move the decimal place to the left to create a new number from 1 up to 10.
2.Determine the exponent, which is the number of times you moved the decimal.
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3 0
3 years ago
Please help i dont get it
Vlad1618 [11]
Hello,

The mean is the average.

Therefore :

\frac{96+84+92+96+100}{5}
=  \frac{468}{5}
=93.6

So the mean of the data set is 93.6.

Hope this helps !

Photon

8 0
3 years ago
Read 2 more answers
Minh wrote the following number sentence 2.6 + 0.33= 59. Use estimation to show that Minh's answer is incorrect.
Ne4ueva [31]
2.6 rounds to 3, and 0.33 would round to 0.50. Adding 3 and 0.50 together would equal to 3.50. 59 and 3.50 are no where near to each other which concludes Minh is incorrect.
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3 0
3 years ago
Suppose that cos = 12/13 what is sin what is cos 2
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cos x = 12/13 is fine; here "cos" has the argument (input) x.

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cos 2 is an entirely different kind of problem.  Here you are told what the argument (input) to the cosine function is (it is 2, which here means 2 radians).

Using a calculator:  cos 2 = -0.416.  Note that the angle 2 rad is in QII, which is why the "adjacent side" is negative and also why the cos of 2 is negative.
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