a)explain how to interpret the result of this study and make a conclusion. b) what does the phrase "the confidence level for this study is 95% mean?

Question

For the confidence interval ($61,$97), indentify the mean and margin of error.  A sample population of 300 subjects was selected by taking a simple random sample of lunch reciepts from the colleges snack bar over the course of a month. the study found that the mean amount of a reciept is $9.35+-$1.10. The confidence level for this study is 95%.

Answer 1

Hi Christina,

 

For confidence intervals (a,b), the mean is just the midpoint (a+b)/2. The margin of error is the distance from the mean to the upper/lower bounds, i.e. b - (a+b)/2 = (2b-a-b)/2 = (b-a)/2. When we talk about confidence intervals for means, if we are using a confidence level of x%, then given a confidence interval, we say that "We are x% confident that the true mean lies between a and b" where a and b are the bounds for the confidence interval.