The mean work week for engineers in start-up companies is claimed to be about 64 hours with a standard deviation of 7 hours. Kara, a newly hired engineer hopes that it's not (she wants it to be shorter). She asks 10 engineers in start-ups for the lengths of their mean work weeks. Their responses are 70; 45; 55; 60; 65; 55; 55; 60; 50; 55.

a. Is the newly hired engineer testing a mean or a proportion?

• proportion
• mean

b. The null hypothesis (or company claim), in symbols, is =____________

.

c. If the claim is correct, what is the probability that a sample mean would be as low as Kara's mean?

_____________ %

Give your answer as a percentage accurate to one decimal place.

d. If Kara will accept the 64 hours as the real average so long as there's at least a 10% chance the sample average value could be as low as hers, should she accept the claim?

• yes
• no