SOLUTION: A researcher is interested in whether students who attend private high schools have higher average SAT scores than students in the general population of high school students. A ran

Question 1168096: A researcher is interested in whether students who attend private high schools have higher average SAT scores than students in the general population of high school students. A random sample of 90 students at a private high school is tested and has a mean SAT score of 1,050. The average for public high school students is 1,000 (σ = 200).
9.Determine the 95% Confidence Interval for the population mean, based on the sample mean.
I got 1008.68 - 1091.32 am i correct?

Question 10 is based on the following data:
The producers of a new toothpaste claim that it prevents more cavities than other brands of toothpaste. A random sample of 60 people uses the new toothpaste for six months. The mean number of cavities at their next checkup is 1.5. In the general population, the mean number of cavities at a six-month checkup is 1.73 (σ = 1.12).
10.Determine the 95% Confidence Interval for the population mean, based on the sample mean.
I need help solving this question
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
the half-interval is 1.96*200/sqrt(90), and that is added to and subtracted from, the mean.
that is 41.32, so yes, you are correct.
same approach--the half-interval is 1.96*1.12/sqrt(60)=0.2834
the interval is 1.5+/-0.28 or (1.22, 1.78) units cavities
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