A postal worker randomly selected packages that were processed at the staffed counter and packages that were p

A postal worker randomly selected packages that were processed at the staffed counter and packages that were processed at the self-serve station and recorded their weights. The table shows the results.


counter......self-serve
n=51....n=39
x(with bar on top of x)= 14.5lb....x(same)=6.4lb
s=3.1lb.....s=1.3lb


there is a 90% probability that packages processed at the counter weigh between 7.3 lb and 8.9 lb more than packages processed at the self-serve station.
there is a 90% probability that packages processed at the self-serve station between 7.3 lb and 8.9 lb more than the packages processed at the counter.
there is a 90% probability that packages processed at the counter weigh between 7.6 lb and 8.6 lb more than packages processed at the self-serve station.
there is a 90% probability that packages processed at the self-serve station between 7.6 lb and 8.6 lb more than the packages processed at the counter.

Betsy -

This is a 2-Sample T-Test (non-pooled)

The formulas are complex especially the calculation of the degrees of freedom = 70.72 in this problem. Most students will use their TI-83 or 84 for any two-sample mean problem.

there is a 90% probability that packages processed at the counter weigh between 7.3 lb and 8.9 lb more than packages processed at the self-serve station.

If you have questions on this, email me.

Hope that helps