Please answer the following questions and add a reference to the question:

Q1: You own a Pepsi bottling plant, and you are concerned about filling the bottles to the correct level. Should you conduct a one-tailed or two-tailed hypothesis test? Explain.

For the next set of questions I will provide the original question then the answers from my peers. For each peer question I need to give a substantive feedback as well as ask them a follow-up question on something they may not have answered in there response. I will need a Reference to back up my statement.

Original Question: A research firm tracks the average highway speed of 30 drivers driving home on Day 1. For the next 10 days, the drivers are given two cups of coffee 1 hour before the drive home. On the 10th day, the average highway speed is measured again. Does this study involve dependent or independent samples? You are interested in knowing if there is a statistical difference in driving speeds between Day 1 and Day 10. Which statistical test would be appropriate? Why?

Peer Response 1: This study involves dependent samples. Dependent samples are characterized by a measurement or intervention and another measurement (Lind, Marchal & Wathen, 2015). Its easiest to think of dependent samples as a before and after study. In this example, the 2 samples are driving speeds before the coffee was given (Day 1) and after the coffee was given (Day 2-10).

To determine whether there is a statistical difference in driving speeds between day 1 and day 10, a t-test would be utilized. We are examining the two population means of two small samples (30 drivers). My null and alternative hypothesis of the t-test would be

Ho; U before = U after (mean driving speeds on day 1 are equal to mean driving speeds on day 10).

H1; U before does not equal U after (the mean driving speeds on day 1 does not equal the mean driving scores on day 10).

Peer Question 2: This will be a dependent variable because the samples are taken from the same distribution. This will be a t- test because it is only 30 samples. A sample more than 30 would require a Z-test. If the values in one sample affect the values in the other sample, then the samples are dependent. If the values in one sample reveal no information about those of the other sample, then the samples are independent.

Peer Question 3: What are those conditions for using z-test and t-test as a researcher that you must check? How would you write the hypothesis for difference of means that you are interested in testing in this scenario?