A fallacy is a mistaken belief, particularly one based on unsound arguments or one that lacks the evidence to support it. Common types of fallacy that may compromise the quality of your research are:
Correlation/causation fallacy: Claiming that two events that occur together have a cause-and-effect relationship even though this can’t be proven
Ecological fallacy: Making inferences about the nature of individuals based on aggregate data for the group
The sunk cost fallacy: Following through on a project or decision because we have already invested time, effort, or money into it, even if the current costs outweigh the benefits
The base-rate fallacy: Ignoring base-rate or statistically significant information, such as sample size or the relative frequency of an event, in favor of  less relevant information e.g., pertaining to a single case, or a small number of cases
The planning fallacy: Underestimating the time needed to complete a future task, even when we know that similar tasks in the past have taken longer than planned