- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 1 (55.87 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 2 (21.53 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 3 (39.8 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 4 (39.83 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 5 (33.48 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 6 (15.69 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 7 (15.87 KiB) Viewed 138 times
- E D Weed1 Weed3 2 5 2 1 2 1 2 7 A B 1 Humboldt Oregon 2 16 16 4 B 7 4 17 6 4 15 8 8 9 5 14 5 20 4 6 7 8 9 8 7 14 2 10 7 8 (32.82 KiB) Viewed 138 times
. POWER and Sample size for a 2-Sample test: Steps 1-5: For the following problem run a brief 2-sample t-test with the assumption of equal variances. • Use R code as shown in the example at the end of lecture in Week 12 Day 1. . Consider your hypothesis test as a pilot study and the prompt of the data collector to determine the direction of your one tailed test. Step 6: Then determine the power of the test you just ran. Step 7: Interpret the power value with an English sentence. Step 8: Then determine the optimal sample size that would provide for a level of significance of a = 0.05 and a power of 1-B = 0.80 for a follow-up study. . .
A Grouping of Channeled Whelks 24.3) A graduate student proposes for her Senior project that the whelk density on the coast of Humboldt County are smaller than that found off the Central Oregon coast. She begins with a pilot study at 8 random locations on the Humboldt county coast and 6 random locations off the Oregon coast. At each site she submerges a frame of 0.25 square meters on the sea floor at high tide and counts the number of whelks present within each frame. Does the Humboldt county coast have a smaller population density of whelks than that found off the Oregon coast? image by Marie Gardner . Image source from www.focusonnature.com: Channel Whelks 24.3) Step 1: Preliminary Checks . The data sets are collected from independent and random samples. • We assume that both data sets pass a normality test by the Anderson-Darling normality test, as we are using mean values.
24.3) Step 2 Declare the variables for this hypothesis test: A c 2 3 English text equivalence with special symbols and the raw data set: Special English Text B Note! Because of the limitations in Character Equivalence 1 Humboldt Oregon H. H2 mu-1, mu-2 16 16.4 software most special characters 17.12 eta-1, eta-2 7.4 cannot be included in a pop-up 17.6 o az sigka 1, sigma-2 4 15.8 answer format and yet they are needed 145 P. P2 D-1,D 2 for the hypothesis formation. The pop- 7.8 x-bar-1, x bar-2 10.7 up selections will be in the text-form for Xi, x. x-tilde-1, x-tilde-2 the special characters embedded within PP2 phat-1, p hat-2 the pop-up answer. Use the table at the 10 not equal right as a guide if needed. s D Weedt 21 2.1 27 24 1.8 2.9 2.4 23 89 20.4 9.8 5 ž, že ON E Weeds 25 2.1 1.9 22 23 1.9 2 22 2.4 25 214 23 142 17.5 7.4 NN 2.2 + > or 11 12 13 <o- 24.3) Step 2 Declare the variables for this hypothesis test: mu-1 = The mean density of whelk population on the Humboldt county per 0.25 m coast mean mu-2 ✓ The per 0.25 m2 density of whelk population on the central Oregon coast
24.3) Step 3) Choose the correct hypothesis statement to test the graduate student's claim that the Humboldt county coat has a smaller whelk density than the central Oregon coast. Test the hypothesis at a 10% LOS. H: mu-1 mu-2 Ha: mu-1 mu-2 a= 0.10 24.3), Step 4) Write a statistical conclusion for the hypothesis using output from R for a two-sample t-test with pooled variances At the 10% LOS we Do Not Reject the null hypothesis of H., because: t-Notation and di Support trample -0.572 and df - 12 D.Notational Support: p> va Numeric p= 0.2889 0.10 Validation 24.3), Step 5) Write an English sentence conclusion The evidenco supports the case that Humboldt county coast does not have a lower wholk density than that of the central Oregon coast.
POWER and Sample size for a 2-Sample test: • Consider the hypothesis test run in problem HW 24.3 as a pilot study. • Step 6: Then determine the power of the test you just ran. Step 7: Interpret the power value with an English sentence. • Step 8: Then determine the optimal sample size that would provide for a level of significance of a = 0.05 and a power of 1- B =0.80 for a follow-up study. .
24.3) Step 6: Calculate the power of the two-sample t-test from problem HW 24.3. First find the associated 2-sample with accuracy to the fourth decimal: Z-sample = • Now round the Z-score down to the second decimal and find the associated probability in the Z-table. Power = Q
24.3) Step 7: Interpret the power of the test. Use a power probability rounded to the nearest percentage point to give meaning to the interpretation If the mean whelk density on the Humboldt county coast is significantly less than the mean whelk density on the central Oregon coast, then the two sample t-test used at these small samples will detect that Humboldt county coast whelk density is sparser v in % of all random sample comparisons. (Round your percentage to the nearest integer!) 24.3) Step 8: Determine the optimal sample size that would provide for a level of significance of a = 0.05 and a power level of 1- B -0.80 for a follow-up study The number of 0.25 m2 Humboldt county coast whelk sample plots that would be needed for a follow-up study is ni The number of 0.25 m2 central Oregon coast whelk sample plots that would be needed for a follow-up study is 12