eview Test. Test 3 Test Score: 36.25%, 725 of 20 p 10of20 core: 0.25 of 1 pt 5.4
ID: 3361620 • Letter: E
Question
eview Test. Test 3 Test Score: 36.25%, 725 of 20 p 10of20 core: 0.25 of 1 pt 5.4.38 are normally distrbuted You select 100 tires at random and test that the ife span ofits tres53,000 miesYou workfor aconsumer protection agency and you are testing these Sros. Assume the iHe spans of the tres them The mean ife span is 52.824 mies Assume -TO Complete parts (a) through (c). tho manufacturer's clam·iscorect, what s to potabity that fomeanofhesample is 52,824 mles or less? 0 0080 (Round to four decimal places as needed ) (b) Using your answer from pat (a), what do you think of he manufcturer's dlaim The claim is inacouate the (c) Asauming the mandfacturer's claim is true, would it be unusual to have an individual tive with a lHe span of 52,824 miles? Why or why norh No ,because 52,824 les because the sample mean wouid be considened unusual since i does not le wihin the within te range of a usual event, namely within 2 standard deviationa of the mean for an individual treExplanation / Answer
Solution:
(a) From the given information
Standard error = sd /sqrt(n) = 700/sqrt(100) = 70
Z value for 52,824, z = (52,824-53000)/70 = -2.51
P( mean x < 52,824) = P( z < -2.51)
= 0.006
(b) The claim is accurate inaccurate because the sample mean would be considered unusual since it does not lie lies within the range of a usual event, namely within 1 standard deviation 2 standard deviations 3 standard deviations of the mean of the sample means.
(c) Yes , because 52,824 does not lie within the range of a usual event, namely within 1 standard deviation 2 standard deviations 3 standard deviations of the mean for an individual tire.
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