Answer:
B: Yes, the participants are grouped by sun exposure, and then both treatments are randomly assigned within each group.
Step-by-step explanation:
Randomized block design is one in which the experimental units are categorized into groups which we call blocks. Thereafter, treatments will be randomly allocated to the experimental units inside each of the blocks.
Now, from the question, we can see that they were grouped in Blocks according to their outdoor activity which is degree of exposure to the sun. Thereafter the individual groups are randomly assigned treatments.
Thus, Option B is correct.
Questions:
A clothing manufacturer uses the model a = √(f + 4) - √(36 - f) to estimate the amount of fabric to order from a mill. In the formula, a is the number of apparel items (in hundreds) and f is the number of units of fabric needed. If 400 apparel items will be manufactured , how many units of fabric should be ordered?
Answer:
32 units of fabrics
Step-by-step explanation:
Given

Required
Find f when a = 4
Substitute 4 for a

Rewrite as:

Square both sides



Collect Like Terms


Divide through by 2

Square both sides




Collect like terms


Factorize

or 
f can not be 0 because some units must be ordered.
So, f = 32
D. All students in each grade. It can't be A since the survey is for the students, it defeats the purpose. It can't be B and C since those are too biased. Basing the student population on one factor like gender and sports is not logical in the context of this survey.