What type of bias is illustrated when a person collects data by observing the flow of traffic and includes personal opinions instead of what they actually observed?

The correct answer is identified as an error of observation. This type of bias occurs when the data collected is influenced by the observer's subjective interpretations or opinions rather than objective measurement of actual events. In the scenario given, the individual is observing traffic flow, which should be a quantitative measure based on facts, such as the number of vehicles passing at a given time. However, by allowing personal opinions to filter into the observations, the integrity of the data is compromised.

This phenomenon illustrates how individual perceptions can cloud objective data collection. An error of observation can lead to conclusions that do not align with the actual data, making any resulting analysis unreliable.

The other options highlight different kinds of biases that, while distinct, do not apply in this scenario. For instance, confirmation bias involves favoring information that confirms one's preexisting beliefs, but the situation described is more about the unreliability of observations rather than a selective affirmation of biases. Selection bias refers to how certain individuals or data points are chosen for inclusion in a study, leading to systematic differences in the results. Measurement error typically refers to inaccuracies in how a variable is quantified, but this does not capture the idea of skewed personal interpretation present in this case.