# Math Help - Statistics

1. ## 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?

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

while the unbiased estimate of $\sigma^2$ is the sample variance ${\sum_{i=1}^n(X_i-\bar X)^2\over n-1}$

3. But I doesnt have n? X would be 4?

And 0,05, what´s that?

4. 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.

5. 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?