Measurement bias caused by observer expectations can be avoided by using observers.

Naive.

Explanation:

Naive observer may be defined as the observer that are unaware of the experimental condition or the study purpose of the experiment. They do not know the effect of the observation period during the experiment.

The data collected and obtained by the naive observer is not likely to be influenced by the observer. They do not influence the observer's expectation and can be avoided by the measurement observer.

Thus, the correct answer is naive.

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