QUESTION 2 Do not forget to justify step by step how you are choosing the test For each test (if there are several) what are the null and alternative hypotheses, the numbers of relevant degree(s) of freedom, the level, the critical value from the proper table(s), the test value calculated from the data, the statistical conclusion, the conclusion for the scientist doing the study. Details of the calculations, if there are errors of calculation you will not loose points If you choose the wrong test you will loose points If you do not justify the test you will loose points If you to not follow #1 and #2 you will loose point If you do not follow #2 at all you will not have a passing grade If you follow 1-7 to the letter - even with calculations error and the wrong test(s) you will at minimum have C- If you follow 1-7 to the letter with only calculations errors and the rest being correct, you will earn A- If you follow 1-7 AND have no calculation errors you will earn A To try to show that trees do no increase the amount of water available for plants, you ask farmers in your family to divide their farms into 2 halves that are as similar as possible, in one half, your family members will continue to farm like they have always done control sample, in the other half trees sample, your have them planting a very diverse assortment of trees, and they are to grow the same crops than in the first half, between the trees. The scientists suggest you do not start recording data in the first 5 years to have time to train all of the people involved in the study, and let the systems start to work. The main measurement is the soil moisture on each half of the farms, soil moisture is measured with a special instrument that gives numbers from 1- 100 usually. These are the results you obtain on the first year data is recorded (you can use the empty columns for calculations):

QUESTION 2

1. 1. Do not forget to justify step by step how you are choosing the test

   2. For each test (if there are several)

      1. what are the null and alternative hypotheses,

      2. the numbers of relevant degree(s) of freedom,

      3. the level, the critical value from the proper table(s),

      4. the test value calculated from the data,

      5. the statistical conclusion,

      6. the conclusion for the scientist doing the study.

   3. Details of the calculations, if there are errors of calculation you will not loose points

   4. If you choose the wrong test you will loose points

   5. If you do not justify the test you will loose points

   6. If you to not follow #1 and #2 you will loose point

   7. If you do not follow #2 at all you will not have a passing grade

   8. If you follow 1-7 to the letter - even with calculations error and the wrong test(s) you will at minimum have C-

   9. If you follow 1-7 to the letter with only calculations errors and the rest being correct, you will earn A-

   10. If you follow 1-7 AND have no calculation errors you will earn A

   To try to show that trees do no increase the amount of water available for plants, you ask farmers in your family to divide their farms into 2 halves that are as similar as possible, in one half, your family members will continue to farm like they have always done control sample, in the other half trees sample, your have them planting a very diverse assortment of trees, and they are to grow the same crops than in the first half, between the trees. The scientists suggest you do not start recording data in the first 5 years to have time to train all of the people involved in the study, and let the systems start to work. The main measurement is the soil moisture on each half of the farms, soil moisture is measured with a special instrument that gives numbers from 1- 100 usually.

   These are the results you obtain on the first year data is recorded (you can use the empty columns for calculations):

   	Control	Trees
   Farm 1	13.1	13.8
   Farm 2	14.8	51.3
   Farm 3	21.1	28.8
   Farm 4	33.4	28.8
   Farm 5	31.8	39.3
   Farm 6	33.3	27.2
   Farm 7	20.8	73.4
   Farm 8	9.9	13.6
   Farm 9	2.2	16.4
   Farm 10	31.4	29.9
   Farm 11	15.2	63.1
   mean	20.6	35.1

   1. Both samples were tested with the shapiro wilks test, the smallest p-value was above 0.17. What do you conclude from that ? (do not forget to explain what the shapiro wilks test is for, what are the null and alternative hypotheses, what is the conclusion of the test, and what that means for you, when you are analysing the data.

   2. There are 3 very important clues in the first paragraph, to help choose the proper test from the 4 tests we know that can deal with comparing 2 different means. List the 3 clues?

   3. Conduct the proper statistical test to see if smoking and incontinence are independent variables. Dont forget to satisfy the step 1-7 from the disclaimer at the beginning of the exam.

QUESTION 3

1. BONUS: (complement of Q2

   The United Nation hears about your study, and start to work with you to recruit more farmers in different area that could benefit from the results of a serious large scale study. You end up having 173 farms in 10 countries. Some of the farms will not be making the swales on contour, and instead of dividing the farms in 2 halves, the entire farms are dedicated to 4 possible set up :

   1. trees are planted, and crops are grown between them,

   2. the farmers continue their practice as before, no trees are planted

   3. Swales on contour are built, but no trees are planted

   4. Both swales on contour are built, and trees are planted on top

   What test would you use to analyze the soil moisture data in this case ?