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Engine parts Here are measurements (in millimeters) of a critical dimension on an SRS of 16of the more than 200auto engine crankshafts produced in one day:

224.120, 224.001, 224.017,223.982,223.989,223.960,224.089,223.987,223.976,223.902,223.980,224.098,224.057,223.913,223.999

(a) Construct and interpret a 95%confidence interval for the process mean at the time these crankshafts were produced.

(b) The process mean is supposed to be =224but can drift away from this target during production. Does your interval from part (a) suggest that the process mean has drifted? Explain.

- Determine the sample size required to obtain a level Cconfidence interval for a population mean with a specified margin of error.

Short Answer

Expert verified

(a) The sample is 3535

(b) Yes

Step by step solution

01

Part (a) Step 1: Given Information

Given in the question that,

224.120
224.001
224.017
223.982
223.989
223.961
223.960
224.089
223.987
223.976
223.902
223.980
224.098
224.057
223.913
223.999

we have to construct and interpret a 95%confidence interval for the process mean at the time these crankshafts were produced.

02

Part (a) Step 2:  Explanation 

The formula to compute the confidence interval is:

x-t2sn<<x+t2sn

The confidence interval using Ti-83calculator could be computed as:

Thus there is95%probability that the population mean is between223.97and227.03

03

Part (b) Step 1: Given Information 

The process mean is supposed to be =224 but can drift away from this target during production .we have to find that Does interval from part (a) suggest that the process mean has drifted .

04

Part (b) Step 2:  Explanation 

From the above part, it is known that the population mean process is between 223.97and224.03Since, the interval is containing 224 it could be said that the process mean has drifted.

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Most popular questions from this chapter

The weights (in pounds) of three adult males are 160,215and195. The standard error of the mean of these three weights is

(a) 190

(b) 27.84

(c) 22.73

(d) 16.07

(e)13.13

6. Auto emissions Oxides of nitrogen (called NOXfor short) emitted by cars and trucks are important contributors to air pollution. The amount of NOX
emitted by a particular model varies from vehicle to vehicle. For one light-truck model, NOXemissions vary with mean that is unknown and standard deviation =0.4gram per mile. You test an SRSof 50of these trucks. The sample mean NOXlevel xestimates the unknown . You will get different values of xif you repeat your sampling.

(a) Describe the shape, center, and spread of the sampling distribution of x.
(b) Sketch the sampling distribution of x. Mark its mean and the values one, two, and three standard deviations on either side of the mean.
(c) According to the 689599.7rule, about 95%of all values of xlie within a distance mof the mean of the sampling distribution. What is m? Shade the region on the axis of your sketch that is within m of the mean.
(d) Whenever xfalls in the region you shaded, the unknown population mean lies in the confidence interval xm. For what percent of all possible samples does the interval capture ?

I collect an SRS of size n from a population and compute a 95%confidence interval for the population proportion. Which of the following would produce a new confidence interval with larger width (larger margin of error) based on these same data?

(a) Use a larger confidence level.

(b) Use a smaller confidence level.

(c) Increase the sample size.

(d) Use the same confidence level, but compute the interval n times. Approximately5% of these intervals will be larger.

(e) Nothing can guarantee absolutely that you will get a larger interval. One can only say that the chance of obtaining a larger interval is 0.05.

Teens' online profiles Over half of all American teens (ages 12 to 17 years) have an online profile, mainly on Facebook. A random sample of 487 teens with profiles found that 385 included photos of themselves. 13

(a) Construct and interpret a 95%confidence interval for p. Follow the four-step process.

(b) Is it plausible that the true proportion of American teens with profiles who have posted photos of themselves is 0.75? Use your result from part (a) to support your answer.

The news article goes on to say: 鈥淭he theoretical errors do not take into account a margin of additional error resulting from the various practical difficulties in taking any survey of public opinion.鈥 List some of the 鈥減ractical difficulties鈥 that may cause errors in addition to the 3percentage point margin of error. Pay particular attention to the news article鈥檚 description of the sampling method.

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