1.) You measure the lifetime (in miles of driving use) of a random sample of 25
ID: 3149596 • Letter: 1
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1.) You measure the lifetime (in miles of driving use) of a random sample of 25 tires of a certain brand. The sample mean is 64,200 miles. Suppose that the lifetimes for tires of this brand follow a normal distribution, with unknown mean and standard deviation = 4,800 miles. You wish to estimate the mean lifetime for all tires of this brand. This problem calls for?
A) a confidence interval for
B) a hypothesis test for
C) a randomized comparative experiment.
D) a stratified random sample.
Information: A bottling plant produces 1 liter bottles of soda. The actual distribution of volumes of soda dispensed to bottles is Normal, with mean and standard deviation = 0.05 liter. W randomly select 6 bottles and measure the volume of soda in each. The results of these 6 measurements (all in liter units) are 1.05 1.04 1.01 1.06 0.94 0.99.
2.) Based on these data, the margin of error for a 90% confidence interval is
A) 1.015
B) 0.033
C) 0.028
D) 0.94
3.) Which of the following is true?
A) In taking many, many random samples of 6 bottle volumes, each time computing a 90% confidence interval for the average volume, 90% of our confidence intervals will capture .
B) There's a 0.90 probability that is contained in the interval computed in the 90% confidence interval previously computed.
C) If we construct 10 confidence intervals for , each based on a random sample of 6 bottle volumes, exactly 9 of them will capture .
D) All of the above.
4.) The critical value, z*, used for constructing a 96% confidence interval for a population mean is
A) 2.326.
B) 1.645.
C) 2.054.
D) 2.576.
5.) I collect a random sample of size n from a population and from the data collected compute a 95% confidence interval for the mean of the population. Which of the following would produce a new confidence interval with larger width (larger margin of error) based on these same data?
A) Use the same confidence level, but compute the interval n times. Approximately 5% of these intervals will be larger.
B) Use a smaller confidence level.
C) Use a larger confidence level.
D) Nothing can guarantee absolutely that you will get a larger interval. One can only say the chance of obtaining a larger interval is 0.05
Explanation / Answer
1) WE HAVE BEEN GIVEN THE STANDARD DEVIATION AND THE MEAN LIFE OF 25 TIRES AND WE NEED TO ESTIMATE THE MEAN LIFE OF ALL THE TIRES OF THIS BRAND THEN THE REQUIRED THING TO BE DONE IS TO FIND THE CONFIDENCE INTYERVAL OF THE TIRES . AS CONFIDENCE INTERVAL GIVES THE ESTIMATED THAT THE MEAN OF THE TIRES LIFE WILL BE IN THE INTERVAL ONLY. THEREFORE THE OPTION A IS CORRECT.
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