The CEO of a large manufacturing company is curious if there is a difference in productivity level of her warehouse employees based on the region of the country the warehouse is located. She randomly selects 35 employees who work in warehouses on the East Coast (Group 1) and 35 employees who work in warehouses in the Midwest (Group 2) and records the number of parts shipped out from each for a week.

She finds that East Coast group ships an average of 1276 parts and knows the population standard deviation to be 347.

The Midwest group ships an average of 1439 parts and knows the population standard deviation to be 298.

Using a 0.01 level of significance, test if there is a difference in productivity level. What is the test statistic?