MHB Confidence intervals and point estimate problems

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To determine the sample size used in a study with a 99% confidence interval of 152 to 158 and a standard deviation of 10, the calculation involves using the formula for the margin of error, which leads to a sample size of approximately 36. For the second problem, the point estimate of the proportion of students responding "no opinion" can be calculated by dividing the number of "no opinion" responses by the total number of responses, resulting in a proportion of 0.05. The discussions highlight the need for clarity in applying statistical formulas to solve confidence interval and point estimate problems. Participants express a desire for guidance on these calculations, emphasizing a common struggle with understanding statistical concepts. Overall, the thread seeks assistance in navigating these statistical challenges.
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I am lost on how to do these two problems and can't find info on how to solve them anywhere. If anyone can get me on the right track as to how to start, that would be amazing!

1. A 99% confidence interval for a population mean was reported to be 152 to 158. If the standard deviation is 10, what sample size was used in this study?

2. A survey for a sample of 300 students resulted in 175 yes responses, 110 no responses, and 15 no opinions. What is the point estimate of the proportion in the population who respond "no opinion"?
 
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colle said:
I am lost on how to do these two problems and can't find info on how to solve them anywhere. If anyone can get me on the right track as to how to start, that would be amazing!

1. A 99% confidence interval for a population mean was reported to be 152 to 158. If the standard deviation is 10, what sample size was used in this study?

As reported in...

http://mathhelpboards.com/questions-other-sites-52/unsolved-statistics-questions-other-sites-part-ii-1566-post12072.html#post12072

... is [approximately] $ \text{erfc}\ (x) = .01$ for $x \sim 1.8$ so that is $\displaystyle \frac{10}{\sqrt{n}} = \frac{5}{3} \implies n=36$... Kind regards $\chi$ $\sigma$
 
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