Reading the buret volume by looking up at the liquid level is an example of which error type?

• A. Random error
• B. Instrumental error
• C. Systematic error
• D. Methodological error

Answer: (D)

Parallax error is at play here. When you read a buret, the level you perceive depends on the angle of your eye relative to the scale. Looking up at the liquid level from above causes the meniscus to appear at a different mark than its true position, introducing a consistent bias in the measurement. This bias arises from the observation technique rather than from the instrument itself or from random fluctuations, so it’s best described as a methodological error. To avoid it, read with your eye level with the meniscus and directly at the scale, ensuring you view perpendicular to the scale.