Example •A95% confidence interval for the mean speed of cars on a highway is to be constructed which must be accurate to within 2 miles per hour. Assume the population standard deviation is 9 miles per hour. What size sample is required? • If the maximum error is 1 mile per hour...
This means that if we repeatedly compute the mean (M) from a sample, and create an interval ranging from M - 23.52 to M + 23.52, this interval will contain the population mean 95% of the time. In general, you compute the 95% confidence interval for the mean with the following formula...
内容提示: Confidence Interval 1. After surveying students at Dartmouth College, a campus organization calculated that a 95% confidence interval for the mean cost of food for one term. Now the organization is trying to write its report, and considering the following interpretations. Comment on each...
Formulaforaz-confidenceinterval: Supposeyouworkforaconsumeradvocateagency&wanttofindthemeanrepaircostofawashingmachine.Yourandomlyselect40repaircostsandfindthemeantobe$100.Thestandarddeviationis$17.50.constructa95%intervalforthepopulationmean. Findtheminimumrequiredsamplesizeifyouwanttobe95%confidentthatthesamplemean...
This comparison demonstrates that the use of the approximate confidence interval can markedly underestimate the upper limit of the confidence interval when n is small and if SL is above 3 dB(A). 展开 关键词: confidence intervals lognormal distribution occupational noise exposure sampling ...
This chapter explains how to find the 95 % confidence interval about the mean for a set of data, and how to test hypothesis about your data using this confidence interval. You will learn how to estimate the population mean (average) for a group of people (or objects) at a 95 % ...
It is counterintuitive that, with a sample of only one value from a normal distribution, one can construct a finite confidence interval of any size for the mean. It goes just as much against standard teaching that from a sample of size two such a CI might be shorter than that based on ...
Step 3: use that Z value in this formula for the Confidence Interval:X ± Zs√nWhere:X is the mean Z is the chosen Z-value from the table above s is the standard deviation n is the number of observationsAnd we have:175 ± 1.960 × 20√40...
For the case of the confidence interval for a population mean, you need the normality assumption met, which means that the sample is drawn from a normally distributed population. Also, in order to use the above formula we need to have that the population standard deviation is known. ...
Problem: Psychologists recorded the size of the tip of25patrons in a restaurant when a message indicating that the next day's weather would be good was written on their bill. We know that the population standard deviation isσ=2.2.We ...