Question

Statistics
37 packages are randomly selected from packages revived by a parcel service. the sample has a mean wight of 17 pounds and a standard deviation of 3.3 pounds. What is the 95% confidence interval for the true mean weight of all pacakges?

Answer 1

first find the standard error:
\[\sigma = \frac{3.3}{\sqrt{37}} \approx 0.5425\]
95% confidence interval will be +- 2 std errors
\[17 \pm 2(.5425)\]

Answer 2

im sorry i am incorrect ...i just checked something
it should be "1.96" times the std error

Answer 3

http://en.wikipedia.org/wiki/Standard_error