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Margaret [11]
2 years ago
15

In order to fairly set flat rates for auto mechanics, a shop foreman needs to estimate the average time it takes to replace a fu

el pump in a car. How large a sample must he select if he wants to be 90% confident that the average time is within 20 minutes of the sample average? Assume the standard deviation of all times is 40 minutes.
Mathematics
1 answer:
Ede4ka [16]2 years ago
4 0

Answer:

ME = 1.96(45)/sqrt(n) 25 = 1.96(45)/sqrt(n) n = (1.96(45)/25)^2 = 6

Step-by-step explanation:

yw

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Lyrx [107]

Answer:

18$

Step-by-step explanation:

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3 years ago
Help again. I’m really bad at this.
siniylev [52]

Given the equation of a circle in the form

(x-x_0)^2+(y-y_0)^2=r^2

You have that (x_0,y_0) is the center, and r is the radius.

So, in your case, the center is (-9,6) and the radius is 5.

6 0
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Find the volume of a cone with the radius of radius of 80 and height of 21
RoseWind [281]

Answer:

140672

Step-by-step explanation:

formula for cone volume=pi*r^2*h*1/3

80^2*3.14*21=422016

422016*1/3

=140672

5 0
3 years ago
The Wisconsin Dairy Association is interested in estimating the mean weekly consumption of milk for adults over the age of 18 in
Stolb23 [73]

Answer:

ME = 1.653 *\frac{7.9}{\sqrt{300}}= \pm 0.75

±0.75 ounce

Step-by-step explanation:

Assuming this complete question: The Wisconsin Dairy Association is interested in estimating the mean weekly consumption of milk for adults over the age of 18 in that state. To do this, they have selected a random sample of 300 people from the designated population. The following results were recorded: xbar=34.5 ounces, s=7.9 ounces Given this information, if the leaders wish to estimate the mean milk consumption with 90 percent confidence, what is the approximate margin of error in the estimate?

Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

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".

\bar X=34.5 represent the sample mean

\mu population mean (variable of interest)

s=7.9 represent the sample standard deviation

n=300 represent the sample size  

Solution to the problem

The confidence interval for the mean is given by the following formula:

\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}   (1)

In order to calculate the critical value t_{\alpha/2} we need to find first the degrees of freedom, given by:

df=n-1=300-1=299

Since the Confidence is 0.90 or 90%, the value of \alpha=0.1 and \alpha/2 =0.05, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.05,199)".And we see that t_{\alpha/2}=1.653

And the margin of error is given by:

ME = 1.653 *\frac{7.9}{\sqrt{300}}= \pm 0.75

±0.75 ounce

4 0
3 years ago
Read 2 more answers
Thanks for the help! Been stuck on this one for a little while.
igor_vitrenko [27]

Answer:

B. \sqrt{14}

Step-by-step explanation:

Since 3.74 is rounded to the hundredths place, it is not the ideal exact solution for m^2 = 14.

To solve for m you would have to square root m and 14, which gives you \sqrt{14}. This is the best answer for the problem.

8 0
3 years ago
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