Question

The scores on an examination in biology are approximately normally distributed with mean 500 and an unknown standard deviation. The following is a random sample of scores from this examination.

404, 438, 475, 508, 522, 576

Find a 99% confidence interval for the population standard deviation. Then complete the table below.
Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal places.

What is the lower limit of the 99% confidence interval?
What is the upper limit of the 99% confidence interval?

Answer 1

The reason that I am confused is because when I calculate this out I come up with a mean of 487.167

Answer 2

I came up with a lower limit of 385.64 and an upper limit of 588.70, based on how I know how to do this problem, but it says I should be using a mean of 500 which is throwing me off.

Answer 3

http://easycalculation.com/statistics/standard-deviation.php

Answer 4

Total Numbers: 6
Mean (Average):487.16667
Standard deviation:61.67793

Answer 5

woops, you want a t confidence interval, since your sample is so small