Suppose a chef claims that her meatball weight is not equal to4

ounces, on average. Several of her customers do not believe her, so the chef decides to do a hypothesis test, at a10% significance level, to persuade them. She cooks13 meatballs. The mean weight of the sample meatballs is3.9 ounces. The chef knows from experience that the standard deviation for her meatball weight is0.6ounces.

• H
• 0
• :=4
• ;H
• a
• :4
• =0.1
• (significance level)

What is the test statistic (z-score) of this one-mean hypothesis test, rounded to two decimal places?