# Confidence Interval

• Jun 17th 2008, 08:26 AM
pbball
Confidence Interval
Hello Everyone,

This is my first time posting. I'm working on a statistics problem that I'm having difficulty understanding. Here is the problem:

The Praxis II test was given to a sample of 1573 prospective teachers. The mean of these scores was 1053 and the standard deviation was 92.
a.) Give a 95% confidence interval (μ ± 2ơ) for the mean (average) score in the population of all young women.
b.) Suppose that a sample of 300 prospective teachers had produced the same mean and standard deviation. Again, give the 95% confidence interval (μ ± 2ơ) for the mean (average) score in this case.

I have gone over and over but I'm not understanding something because it feels like information is missing based on what I have been doing. I appreciate any help with understanding the problem.
• Jun 17th 2008, 12:10 PM
mr fantastic
Quote:

Hello Everyone,

This is my first time posting. I'm working on a statistics problem that I'm having difficulty understanding. Here is the problem:

The Praxis II test was given to a sample of 1573 prospective teachers. The mean of these scores was 1053 and the standard deviation was 92.
a.) Give a 95% confidence interval (μ ± 2ơ) for the mean (average) score in the population of all young women.
b.) Suppose that a sample of 300 prospective teachers had produced the same mean and standard deviation. Again, give the 95% confidence interval (μ ± 2ơ) for the mean (average) score in this case.

I have gone over and over but I'm not understanding something because it feels like information is missing based on what I have been doing. I appreciate any help with understanding the problem.

You will find several worked examples of this type of question on these boards.

In both cases you have the values of n, $\displaystyle \overline{x}$ and $\displaystyle s_x$. You only have to decide whether to use the t- or z-statistic.

Why do you think there is missing information? Where exactly are you stuck?