by Federal Rule of Criminal Procedure 52, which holds, "[a]ny error, defect, irregularity, or variance that does not affect substantial rights must be disregarded, [while a] plain error that affects substantial rights may be considered even though it was not brought to the court's attention." The appellate court has discretion as to whether or not to correct plain error. Usually the court will not correct it unless it led to a brazen miscarriage of justice. Questions of constitutionality Questions of constitutionality are considered a type of question of law, and thus appellate courts always review lower court decisions that address constitutional issues de novo. However, the term "standard of review" has an additional meaning in the context of reviewing a law for its constitutionality, which concerns how much deference the judiciary should give the legislature (i.e., the federal Congress or state legislatures) in determining whether legislation is constitutional. Concerning constitutional questions, three basic standards of review exist: rational basis, intermediate scrutiny, and strict scrutiny. This form of standard of review is sometimes also called the standard or level of scrutiny. These levels of scrutiny are normally applied to legislation, but can also be applied to judicial acts and precedents (as seen in the context of challenges to the constitutionality of awards of punitive damages). In other words, the common law (including case law) is not immune to at least some minimal amount of judicial review for compatibility with the federal Constitution. Rational basis Generally, the Supreme Court judges legislation based on whether it has a reasonable relationship to a legitimate state interest. This is called rational basis review. For example, a statute requiring the licensing of opticians is permissible because it is directed to the legitimate state objective of ensuring the health of consumers, and the licensing statutes are reasonably related to ensuring consumers' health by requiring certain education for opticians. Intermediate scrutiny Under the Equal Protection Clause, when the law targets a "quasi-suspect" classification, such as gender, the courts apply intermediate scrutiny, which requires the law to be substantially related to an important government interest. As the name implies, it is more strict than rational basis review but less strict than strict scrutiny. Other forms of intermediate scrutiny are applied in other contexts. For example, under the Free Speech Clause, content-neutral time, place, and manner restrictions on speech are subject to a form of intermediate scrutiny. Strict scrutiny If