which of the following best describes the purpose of a placebo in an experiment
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LPN Nutrition Practice Test

1. What is the primary purpose of a placebo in an experiment?

Correct answer: D

Rationale: The correct answer is D. A placebo serves as a control for comparison with the treatment group, helping to eliminate bias and ensure the results are due to the treatment itself. Placebos are crucial in research to distinguish the actual effect of the treatment from psychological or subjective factors. Choice A is incorrect because the purpose of a placebo is not related to reducing the cost of the experiment. Choice B is incorrect because while placebos are used in double-blind studies, their primary purpose is not to make the experiment double-blind. Choice C is incorrect because the purpose of a placebo is not to increase the number of participants but rather to serve as a comparison group for the treatment being tested.

2. What does a positive correlation between two variables indicate?

Correct answer: B

Rationale: A positive correlation between two variables indicates that they move in the same direction. This means that as one variable increases (or decreases), the other variable also increases (or decreases). Choice A is incorrect because correlation does not imply causation; it only shows a relationship between variables. Choice C is incorrect as it describes a negative correlation where variables move in opposite directions. Choice D is incorrect as a positive correlation implies a relationship between the variables.

3. What is one characteristic that differentiates vitamins from minerals?

Correct answer: A

Rationale: The correct answer is A. Vitamins are organic compounds, containing carbon, which is a key characteristic that differentiates them from minerals. Choice B is incorrect because vitamins do not provide energy; they are not a source of calories. Choice C is incorrect as both vitamins and minerals are considered micronutrients due to being essential in small amounts. Choice D is incorrect because while it is true that vitamins are needed in small amounts, this is not the characteristic that sets them apart from minerals.

4. What is the primary role of dietary guidelines?

Correct answer: C

Rationale: The correct answer is C: 'To help individuals meet their nutritional needs while reducing the risk of chronic disease.' Dietary guidelines are designed to provide guidance on the types and amounts of food that support good health and reduce the risk of chronic diseases. Choice A has been corrected to mention 'appropriate proportions' instead of 'equal amounts,' as dietary guidelines emphasize balance and variety. Choice B is partially correct, but the primary focus of dietary guidelines is on meeting nutritional needs. Choice D is incorrect because while dietary guidelines may include nutrient recommendations, their primary focus is on overall dietary patterns rather than specific nutrient intake.

5. What is one function of water in the human body?

Correct answer: B

Rationale: The correct answer is B: Water helps transport nutrients and waste products. Water plays a crucial role in the body by aiding in the transportation of essential nutrients to cells and removing waste products. While water is essential for various metabolic processes, it does not provide calories for energy (choice A). Although water can act as a solvent for biological reactions (choice C), its primary function is not as a solvent. Additionally, while water does help in regulating body temperature to some extent, its main role is not to maintain body temperature (choice D).

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