Statistics

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March 5th 2010, 09:10 AM
Lippi86

Statistics

Any of you guys who feeling comfortable with anything of these?
Im really lost

You observe the following sample (rounded) drawn from a normal random variable
X~N(µ,ó²):

22, 19, 14, 15, 20, 20, 21, 14, 19, 18, 15, 14, 15.

a) Use the sample to estimate µ
and ó².
b) Estimate the variance of the sample average ó²ӿ
c) Find a 99% confidence interval for µ
d) Test the null hypothesis H0: µ15 against H0: µ ≠15 with α= 5%
e) Test the null hypothesis H0: µ=µ0 against H0: µ ≠µ with α= 5% for an arbitrary µ0.
f) Find the confidence interval for µ.

g) How are the results in e) and f) related? Why?

Im glad for all kind of answers!
March 5th 2010, 10:44 PM
matheagle

The estimate of $\mu$ is the sample average $\bar X$

while the unbiased estimate of $\sigma^2$ is the sample variance ${\sum_{i=1}^n(X_i-\bar X)^2\over n-1}$
March 6th 2010, 08:14 AM
Lippi86

But I doesnt have n? X would be 4?

And 0,05, what´s that?
March 6th 2010, 08:28 AM
matheagle

Quote:

Originally Posted by Lippi86

But I doesnt have n? X would be 4?

And 0,05, what´s that?

you do need to open up your book
n is the number of observation in your data set
alpha =.05 is the probability of a type one error

You really do need to crack open your book.
March 6th 2010, 09:46 AM
Lippi86

the variance of the sample average ó²ӿ , I cant find that in my book? is it the same as just a plan ó.

because in the qusetion they asking about ó²... and I cant find how Im doing this? maybe it because the book is written in anoter way of doing it? (Speechless)