What type of challenges to jurors does not require a stated reason?

Peremptory challenges allow attorneys to dismiss potential jurors without needing to provide a specific reason. This type of challenge is based predominantly on the attorney's intuition or strategic considerations regarding how a juror might affect the trial's outcome. The law grants each side a certain number of peremptory challenges as a means of securing a jury that they feel embodies a fair chance of achieving a favorable verdict.

In contrast, for cause challenges necessitate a valid, articulated reason for the dismissal, typically based on biases, conflicts of interest, or other factors that could prevent a juror from serving impartially. Judicial challenges and formal challenges are not commonly recognized terms within this context of jury selection within most legal systems, making them less relevant to the question.

Therefore, peremptory challenges stand out as the correct answer since they are expressly designed to be exercised without the need for explanation, emphasizing an attorney's strategic decision-making in the selection of jurors.