Joe is measuring the widths of doors he bought to install in an apartment complex. He measured 72 doors and found a mean width of 36.1inches with a standard deviation of 0.3 inches. To test if the doors differ significantly from the standard industry width of 36 inches, he computes a z-statistic.

What is the value of Joe's z-test statistic?

• 1.81
• -2.83
• 2.83
• -1.81