00:01
For this problem, to begin, i'll note that since we're looking at 95 % confidence, our alpha value is 0 .05.
00:09
Additionally, since we're looking at basically paired changes, we'll be using a t -distribution for creating the confidence interval that will be with n -1, n is 49, so this is going to be with 48 degrees of freedom.
00:23
Now i'll note that the formula for creating the confidence interval is going to be sample mean value plus or minus the t -score for 48 degrees of freedom and a one -tail proportion of half of alpha, so that's one -tail proportion 0 .025, times our sample standard deviation divided by the square root of the sample size.
00:42
Now to find that critical t -value, i oftentimes use a table of values like what you can see here, but we can see that i don't actually have 48 degrees of freedom on here, so i'm using excel, you can use a graphing calculator, there are plenty of online tools for this, i'm just using what i have at hand.
01:03
So we find that that critical t -value is roughly 2 .01, and i only care about the magnitude.
01:09
So at this point we actually have all the information that we need...