# How to construct a 95% confidence interval for μd?

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• Dec 7th 2011, 08:50 PM
Genevieve03
How to construct a 95% confidence interval for μd?
Average scores for a test taken before learning the topic, then the results following:
Before |12|18|25| 9 |14|16|
After |18|24|24|14|19|20|

The problem is: Construct a 95% confidence interval for μd.
At the 1% significance level, can we conclude that the mean scores increase in the after category?

I think I use the equation d +or- t* sd/sqrt n

∑dsquared=?
∑d=?
n=6
df=5
C.I.=95
alpha=.05
I'm not sure if I'm doing it right any help would be greatly appreciated! I have an example of a similar one but I just want to know for sure if I'm on the right track. Thanks!
• Dec 7th 2011, 08:57 PM
pickslides
Re: How to construct a 95% confidence interval for μd?
If your significance is 1%, then $\displaystyle \displaystyle \alpha =0.01$ , do you understand why?

If you are looking for an increase only then you need a one sided interval for the difference in mean.
• Dec 7th 2011, 09:04 PM
Genevieve03
Re: How to construct a 95% confidence interval for μd?
I think that they are two different questions though. Sorry I should have separated them. First, I'm supposed to construct a 95% confidence interval. Then after, I work out the same problem if alpha were 1%. But I'm just not sure if my equation is right. Have been staring at it for too long and I think I'm just making it harder than it is.