You measure the lifetime of a random sample of 64 tires of a certain brand. Suppose that the lifetimes for tires of this brand follow a normal distribution, with unknown mean μ and standard deviation σ = 5 kg. What is the 99% confidence interval?

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Answer 1 · 2017-04-07T06:45:56

Population mean lies in between #mu=barx+1.6125# and #mu=barx-1.6125#

let the Sample mean be #=x#
Sample Standard Deviation #sigma = 5 kg#
Sample size #n=64#

Then -

Standard Error #SE=sigma/sqrtn=5/sqrt64=5/8=0.625#

Population Mean

#mu=barx+-(zxxSE)#
#mu=barx+-(2.58xx0.625)#
#mu=barx+-1.6125#

Population mean lies in between #mu=barx+1.6125# and #mu=barx-1.6125#

Look at the diagram