Population Standard Deviation

[roystonteo via OfficeKB.com]

Dear Experts,

I will need your kind assistance on this. I am very new towards Excel
Functions, hope you have the patience for me. Thank you in advance.

The question is:

A Researcher wants to carry out a test involving the mean for a sample of
size n = 18. She does not know the true value of population standard
deviation, but is reasonably sure that the underlying population is
approximately normally distributed. Should she use a z-test or at-test in
carrying out the analysis?

 

[JE McGimpsey]

This really isn't an XL question.

One key is the sample size...

You may want to look at a beginning statistics textbook.

 

[roystonteo via OfficeKB.com]

Dear JE,

Thanks for your speedy respond.
Sorry i am very new in this. I believe this is about Hypothesis Testing
question?
May i know what are the things i lack off?

This really isn't an XL question.

One key is the sample size...

You may want to look at a beginning statistics textbook.

Dear Experts,

[quoted text clipped - 8 lines]

approximately normally distributed. Should she use a z-test or at-test in
carrying out the analysis?

 

[JE McGimpsey]

Since the question asks only which test to use, it appears to me that
you lack a good understanding of z-tests and t-tests, and when to apply
each.

In addition to any introductory statistics text book, you may have
access to, you could try:

http://wikipedia.org/wiki/Z-test

and

http://wikipedia.org/wiki/Student's_t-test

 

[Mike Middleton]

roystonteo -

For classical statistical inference regarding the population mean, the t
distribution is appropriate when the sample is used to estimate the unknown
population standard deviation (and you are willing to assume that the
population values are normally distributed).

For that situation, the t distribution can be used for any sample size. For
large sample sizes, the t distribution can be approximated by the normal
distribution. The usual guideline has been "30 or more."

- Mike Middleton
Email (e-mail address removed)
Web http://www.MikeMiddleton.com

 

[roystonteo via OfficeKB.com]

Dear JE,

You are right that i have a lack of understanding of z-tests and t-test.
That is the purpose, i am checking if anybody can guide me along this
question.
I need to get it done by today or else i will get killed..

 

[roystonteo via OfficeKB.com]

Dear Middleton,

Thanks for your general introduction. I have just stepped into a new room,
which i still need time to pick up, but i do not have the luxury of time as i
need to complete this question within today.
Any idea to help me, your help will be very much appreciated.

roystonteo -

For classical statistical inference regarding the population mean, the t
distribution is appropriate when the sample is used to estimate the unknown
population standard deviation (and you are willing to assume that the
population values are normally distributed).

For that situation, the t distribution can be used for any sample size. For
large sample sizes, the t distribution can be approximated by the normal
distribution. The usual guideline has been "30 or more."

- Mike Middleton
Email (e-mail address removed)
Web http://www.MikeMiddleton.com

Dear Experts,

[quoted text clipped - 8 lines]

approximately normally distributed. Should she use a z-test or at-test in
carrying out the analysis?