In class this week we've learned about "hypothesis testing", which allows us to answer yes/no questions with a certain confidence. In this week's exercise, we will use a random sample of 30 flights to carry out a hypothesis test.

*Open your data in Excel and answer the following in complete sentences.

1) Step 1 of Hypothesis Test: Write your hypothesis: you might want to start, "I'm testing the (null) hypothesis that the average delay of a flight departing from Oregon airports is at least __________ minutes", OR "I'm looking for evidence to support the (alternative) hypothesis that the average delay of a flight departing from Oregon airports is less than __________ minutes." (of course, you'll need to fill in the blanks with numbers of your own)

2) Set your significance level: alpha = ____%.

3) Select a random sample of 30 flights. It's fine to use the same random 30 rows you picked last week, but they must actually be random. XLSTAT is great at creating a random sample! Be sure to attach a screenshot of your random sample at the end of the project (to take a screenshot, hold down Shift+Command+4 on a Mac, Windows key+Shift+s on a PC).

Simple Random Sampling in XLSTAT

4) Calculate the test statistic from your 30 flights. The formula for the test statistic is given in the lecture slides. Is your test statistic a z-score or t-score?

Hint 1: Remember you're using the sample standard deviation based on the 30 selected flights.

Hint 2: If you're using Word, Insert > Equation will make your life easier as you show your work!

5) Step 4 of Hypothesis Test: what's your conclusion for this test? In other words, would you be able to conclude whether the average delay of a flight departing from Oregon flights is less than _______ minutes. Use either the p-value method or the critical value method to form a conclusion - be sure to report either your p-value or your critical value.

Hint 3: Use either the critical value approach or p-value approach. If you decide to use the critical value approach, what's the critical value for this test? If you're using the p-value approach, calculate the p-value using your 30 selected flights.

6) Repeat (4) and (5), but test the null hypothesis that (exactly) half of flights are on Southwest airlines using a random sample of 30 flights. Again, be sure to show your work clearly!

Hint 4: remember a hypothesis test for the proportion uses a different equation than a hypothesis test for an average!

S No. Delay Time

1 -15

2 -8

3 -15

4 -18

5 -16

6 -12

7 -23

8 -24

9 4

10 -19

11 -12

12 -17

13 -20

14 -9

15 0

16 16

17 -15

18 12

19 -17

20 -5

21 10

22 -7

23 -5

24 -7

25 24

26 -15

27 -23

28 -19

29 -13

30 -17

Total ?

Sample Mean ?

Sample Standard Deviation ?

Can you comment the explanation please?