Final answer:
All of the provided options contribute to error variance: treating participants differently introduces systematic bias, differences in personal characteristics result in natural variability, and measurement error leads to inaccuracies in the data.
Step-by-step explanation:
The contributions to error variance in a dataset or study can come from various sources. Specifically, the options provided in this question all contribute to error variance:
- Treating individual participants differently can introduce systematic bias and variations that are unrelated to the variables being measured.
- Differences in participants' personal characteristics can result in natural variability because these differences can affect the outcome of the study or the measurement.
- Measurement error refers to any errors that occur in taking measurements, which can lead to inaccuracies in the data collected.
Therefore, the correct answer to the question of which of the following contribute to error variance is D) All of the choices.