Question

Malaria is a disease spread by mosquitos. researchers want to test a potential vaccine for the disease, so they plan on recruiting thousands of subjects from each of the 10 countries that are most affected by the disease. the researchers want to use a randomized block design where some subjects receive the vaccine and the rest receive a placebo.

how should the researchers form the blocks?


choose 1 answer:



a

both the subjects and researchers should be kept blind as to which block the subjects are in.



b

subjects in one block should get the vaccine, while subjects in the other block should get the placebo.



c

subjects within each block should live in the same country as each other.



d

each subject should be randomly assigned to a block.



e

subjects within each block should all live in different countries from each other.

Answer 1

Researchers should form blocks such that each block consists of subjects from the same country in a randomized block design for potential vaccine testing for malaria. This method controls for country-specific variables, allowing for an accurate assessment of the vaccine. The correct option is (C).

Step-by-step explanation:

When researchers want to test a potential vaccine for malaria using a randomized block design, subjects within each block should all live in the same country from each other. This method, denoted as option 'c', ensures that environmental and demographic variables that could potentially affect the outcome are kept constant within each block. Thus, the variance within blocks is minimized, and the vaccine's effectiveness can be more accurately assessed by comparing the differences between the blocks.

By having subjects in each block from the same country, researchers control for factors like genetic background, exposure to malaria, local medical practices, and other country-specific variables, making the results within each block as homogenous as possible.

Randomization then ensures that any remaining variability not accounted for by the blocking is equally distributed between the vaccine and placebo treatments, allowing for a fair comparison of their effects on preventing malaria.

Answer 2

Researchers testing a potential malaria vaccine should form blocks by grouping subjects who live in the same country, ensuring environmental factors affecting malaria exposure are homogeneous within each block.

Step-by-step explanation:

The researchers who want to test a potential vaccine for malaria using a randomized block design should form the blocks in such a way that subjects within each block should live in the same country as each other. This strategy takes into consideration the geographical and environmental factors that may affect the incidence and characteristics of malaria.

Answer: c subjects within each block should live in the same country as each other. This approach ensures that each block is somewhat homogeneous in terms of environmental and malaria exposure factors, which can influence the outcome of the vaccine's efficacy tests.