Statistics/Confidence Level - Please Help

[Guest]

Hello.. I'm in my Junior year of university, and as I haven't yet taken Stats, I find myself rather confused about one of my Bio lab assignments. The trouble stems mainly from the fact that I don't understand the underlying concepts of why I have to do these calculations to find Confidence Level, the T-Test, etc. I mean, I don't really understand what these mean and why I have to find them.

In any case, I was doing my calculations and got stuck at the point where I'm supposed to find Confidence Level. I calculated s^2 and SE. My instructions say:

To determine the confidence interval for the mean of a population, add and subtract 2*SE to your sample mean to get the upper and lower confidence limits.

Since I have no experience with this, I have no idea what I'm doing or what the outcome of this should be. I also am confused by the wording (...add and subtract 2*SE to your sample mean..). I understand subtract from... Does this mean X-(2*SE), or is it (2*SE)-X? (X being the mean value, as I don't know how to do the X-bar symbol here)

This is definitely where I'm most hung up on this assignment and any help would be greatly appreciated! Thank you so much in advance!


-- Alena

 

[tkhunny]

The words "add and subtract" are very bad.

Example: From 10, add and subtract 2. 10 + 2 - 2 = 10.

You insructor means, "add to the mean to find the upper bound and subtract from the mean to find the lower bound".

X+(2*SE) is the upper bound of your confidence interval

X-(2*SE) is the lower bound of your confidence interval

 

[Guest]

Thank you very much... that clarification is a huge help. Now to figure out what to do with all these numbers.



-- Alena