question archive The highway fuel economy of a 2016 Lexus RX 350 FWD 6-cylinder 3
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The highway fuel economy of a 2016 Lexus RX 350 FWD 6-cylinder 3.5-L automatic 5-speed using premium fuel is a normally distributed random variable with a mean of μ = 22.25 mpg and a standard deviation of σ = 1.50 mpg. (a) What is the standard error of X¯¯¯ , the mean from a random sample of 36 fill-ups by one driver? (Round your answer to 4 decimal places.) Standard error of X¯¯¯ (b) Within what interval would you expect the sample mean to fall, with 99 percent probability? (Round your answers to 4 decimal places.) The interval is from to
Answer:
a)
standard error of mean=1.5/sqrt(36)=1.5/6=0.25
b)
99% confidence interval for mean
=22.25+/-2.576*0.25
=22.25+/-0.6440
=(21.6060, 22.8940)