Which chart can only detect systematic error?

Which chart can only detect systematic error?

• A. Cusum
• B. Bar chart
• C. Scatter plot
• D. Histogram

Answer: (A)

This question tests the ability to detect systematic error, a consistent bias that develops over time. A Cusum chart works by summing the deviations of each measurement from a target value as tests are performed sequentially. When small, persistent shifts occur in the process mean, the cumulative sum drifts away from zero and will eventually cross decision limits, flagging a sustained bias. This makes it especially sensitive to gradual systematic changes that might be missed if you only look at individual results. The other charts depict data in different ways: a bar chart shows frequencies in categories, not time order; a histogram reveals the distribution shape of results, not any drift over runs; a scatter plot shows the relationship between two variables, not a time-ordered accumulation of error. So, the Cusum chart is the one that can specifically and effectively detect systematic error.

This question tests the ability to detect systematic error, a consistent bias that develops over time. A Cusum chart works by summing the deviations of each measurement from a target value as tests are performed sequentially. When small, persistent shifts occur in the process mean, the cumulative sum drifts away from zero and will eventually cross decision limits, flagging a sustained bias. This makes it especially sensitive to gradual systematic changes that might be missed if you only look at individual results. The other charts depict data in different ways: a bar chart shows frequencies in categories, not time order; a histogram reveals the distribution shape of results, not any drift over runs; a scatter plot shows the relationship between two variables, not a time-ordered accumulation of error. So, the Cusum chart is the one that can specifically and effectively detect systematic error.