A study of 200 insomniacs paid for by the Serta Mattress - 12944

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mareya

mareya

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A study of 200 insomniacs paid for by the Serta Mattress Company found that the average insomniac counted 350 sheep before falling asleep, with a standard deviation of 120. An insomniac is a person who has difficulty falling asleep. Some useful numbers might be:

=NORMSINV(0.89) 1.2265 

=NORMSINV(0.945) 1.5982 

=TINV(0.89,199) 0.1385 

=TINV(0.11,199) 1.6053 

=TINV(0.055,199) 1.9302 

Calculate an 89% confidence interval for the true mean number of sheep counted by insomniacs

 A.  350±13.62 

 B.  350±13.56 

 C.  350±16.38 

 D.  350±10.41 

 
Solution Description

A study of 200 insomniacs paid for by the Serta Mattress Company found that the average insomniac counted 350 sheep before falling asleep, with a standard deviation of 120. An insomniac is a person who has difficulty falling asleep. Some useful numbers might be:

  &nbs