What is the best way to reduce bias in observation?

Correct answer: Recording all results using the same rule

Direct answer: Option C, recording all results using the same rule. Scientific observation must be fair and systematic. First decide the rule for what will be observed and how it will be written; then apply that rule to every result, including results that do not support the expectation. This reduces the observer’s personal preference and makes comparison possible. Option A is wrong because recording only preferred data hides evidence and creates bias. Option B is wrong because unusual data may be important; it should be checked, not secretly removed. Option C is correct because identical rules give every result an equal chance of being recorded. Option D is less suitable because predicting beforehand may create expectation bias; a prediction is not a method for recording observations. Memory cue: fair observation means “same rule, every result.”