willmoore21
Junior Member
- Joined
- Jan 26, 2012
- Messages
- 75
I have created 1000 random samples of size 10, where X~N(8,2). For each sample I have calculated the sample mean, sample variance, (sigma1)^2 and (sigma2)^2.
I want to find a 95% confidence interval for the mean assuming the population variance is known, and a 95% confidence interval for the mean assuming the population variance is unknown.
What formula do I use for these?
I think, given that I am sampling from a normal distribution, for the known confidence interval, would be:
(X1bar X2bar) +- za/2s.e.(X1bar-X2bar) given that the samples are sufficiently small enough.
For unknown, I think it's:
(X1bar X2bar) +- t((n1+n2-2),a/2) s.e(X1bar-X2bar) <<s.e has a tilda over it, also this formula assumes the sigmas are the same.
Is this correct?
[Edit: in context, this is just a tutorial question where I am demonstrating these techniques for revision for finals, it is not a proper investigation or report]
I want to find a 95% confidence interval for the mean assuming the population variance is known, and a 95% confidence interval for the mean assuming the population variance is unknown.
What formula do I use for these?
I think, given that I am sampling from a normal distribution, for the known confidence interval, would be:
(X1bar X2bar) +- za/2s.e.(X1bar-X2bar) given that the samples are sufficiently small enough.
For unknown, I think it's:
(X1bar X2bar) +- t((n1+n2-2),a/2) s.e(X1bar-X2bar) <<s.e has a tilda over it, also this formula assumes the sigmas are the same.
Is this correct?
[Edit: in context, this is just a tutorial question where I am demonstrating these techniques for revision for finals, it is not a proper investigation or report]
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