Hello folks,
I’m really having issues understanding question 6 from Week 4’s quiz. How can we calculate the t-value if we know the sample averages, but we only know one of the sample variances? The lesson shows how to calculate paired t-tests when you know all individual values so that you can calculate the sample variances that you are not given .Is that information missing in this quiz question maybe?
Thx!
Hi MarlosFZ,
The question reads that a researcher conducts a test with 40 participants and obtains the average reaction time (0.95 seconds). The company states that the average reaction time without the energy drinks is 1.05 seconds. The company doesn’t participate in the test and has nothing to do with the participants, which means 1.05 seconds is a population mean without the energy drinks.
So in this case it is not a two sample test. It is a normal left tailed test, where H0 is X_bar = 1.05 and H1 is X_bar < 1.05 (X_bar is the average reaction time with the drinks).
Whoopsie, you are right. I did not consider taking the company’s claim, with the conflict of interests that it entails, as ground truth 
Thank you!