25/ <br/><br/><br/>25/ What is the estimated 95% confidence interval

(CI) of the average difference in blood vitamin D levels between short sleeve shirt and tank top attire amongst US landscapers in ng/mL?
Please note the following: 1) in practice, you as the analyst decide how to calculate the difference in vitamin D levels between time points for a given study participant, and subsequently interpret the aggregated results appropriately in the context of the data, though for the purposes of this exercise the difference is assigned for you as follows. Define the difference as the second minus the first time points, which is common practice, since the plus or minus sign of the resulting difference reflects any change over sequential time; 2) you might calculate a CI that is different from any of the multiple choice options listed below due to rounding differences, therefore select the closest match; 3) ensure you use either the large or small sample CI formula as appropriate; and 4) you may copy and paste the data into Excel to facilitate analysis.
Select one:
a. 7.73 to 12.52 ng/mL
b. 6.96 to 11.27 ng/mL
c. 6.77 to 11.33 ng/mL
d. 7.11 to 13.90 ng/mL

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Screen Shot 2018-04-27 at 9.54.16 AM.png

Time Point 1, Shirts Time Point 2, Tank Tops
Subject Vitamin D [ng/mL] Vitamin D [gg/mL)
1 47.450 61.067
2 40.596 44.886
3 31.919 37.430
4 42.970 56.497
5 36.523 49.473
6 35.006 59.828
7 36.084 45.952
8 41.544 49.131
9 37.052 41.798
10 35.509 60.169
11 37.589 61.233
12 45.468 46.746
13 41.139 55.365
14 38.179 40.634
15 36.460 42.405
16 42.285 41.957
17 38.073 58.163
18 45.759 38.340
19 32.949 45.359
20 30.395 51.438
21 32.841 44.504
22 32.872 53.013
23 36.863 46.583
24 37.999 47.095
25 43.202 48.377
26 37.412 53.241