A principal randomly slected 6 students to take an aptitude test, their scores were 83, 84.1, 83.5, 83.7, 84.1, and 73.5. construct a 90% confidence interval for the mean score for all students. Assume the population has a normal distribution.

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- Dec 14th 2009, 11:29 PMsuperman31confidence interval
A principal randomly slected 6 students to take an aptitude test, their scores were 83, 84.1, 83.5, 83.7, 84.1, and 73.5. construct a 90% confidence interval for the mean score for all students. Assume the population has a normal distribution.

- Dec 15th 2009, 04:16 AMCaptainBlack
Compute the sample mean $\displaystyle m$ and the unbiased estimate from the sample of the population SD $\displaystyle s$.

Then the interval you require is: $\displaystyle (m-\lambda s, m+\lambda s)$ where $\displaystyle \lambda$ is the $\displaystyle 95 \%$ point for the cumulative t-distribution with $\displaystyle n=5$ degrees of freedom.

CB