Just came across this one question asking what 1 - alpha represents? A Level of significance B Confidence interval C Level of confidence very straight but as it seemed to be an easy question, as soon as I saw B I selected B and didnt even read C. Now I am confused answer is C. I dont have issue undertsanding why C is the right answer but rather I d like to know what the difference between B and C is. 1 - alpha isnt it also the confidence interval. Are they not the same thing. ex: Alpha=5% ==> 1- alpha = 95% level of confidence is 95% but so is the confidence interval equivalent to 95% or 1 - alpha. I mean it is not a big deal since I was so suprised that if I have the same question I will remember but still thought it would be interesting to clear my brain out. Thx

The confidence interval is the actual numerical interval…like 50 +/- 2.5 or something like that. Think of the confidence interval as the bookends of the “fail to reject null” portion. The level of confidence is the % term.

so the confidence interval lets say is -1.96 to 1.96 (5% level of significance). This would be the right answer and the fact that it is equivalent to 95% is just a characteristic ofthe interval or in other word the level of confidence for the interval -1.96 to 1.96 is 95%. Thx man

Confidence interval would be sample mean ± 1.96 * std.error. (The actual numerical values).