Question

question 14
there may be only one variable in an experiment.
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question 15
observation is made using tools or measurement.
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question 16
whats the difference between an observation and inference?

Explanation:

For Question 14: In a well - controlled experiment, there is typically one independent variable to determine its impact clearly. For Question 15: Quantitative observation involves using tools or measurements. For Question 16: An observation is a direct perception of a phenomenon, while an inference is a conclusion drawn from observations.

Answer:

Question 14: Independent
Question 15: Quantitative
Question 16: An observation is a direct perception of something (using senses or tools), while an inference is a conclusion or interpretation based on observations.