Question 1187196: A report in a research journal states that the average weight loss of people on a certain drug is 35 lbs with a margin of error of ±3 lbs with confidence level CL = 95%.
(a) According to this information, the mean weight loss of people on this drug, 𝜇, could be as low as ___ lbs.
(b) If the study is repeated, how large should the sample size be so that the margin of error would be less than 1.5 lbs? (Assume 𝑆= 8 lbs.)
ANSWER:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! 32 pounds, the mean- the margin of error
margin of error is t*s/sqrt(n)=3 pounds.
check to see if what the original sample size was with s=8
t (df unknown, 0.975) is about 2 for unknown sample size*8/sqrt(n) and has to equal 3
16/sqrt(n)=3; sqrt n=(16/3) n=256/9 or about 28.
error=t*s/sqrt(n);
1.5 pounds=2*8/sqrt(n), guessing the value of t
square both sides
2.25=256/(n)
n=256/2.25, or 114 rounded up.
that is the answer given the t with df=113 is very close to 2.
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