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A footrace longer than the $26.2$ miles of a long-distance race is known as an ultra-long-distance race.

The random assignment method assigns subjects to treatments based on chance. Before the treatments are applied, random assignment establishes treatment groups that are comparable (except for chance variance). In experiments, randomization and comparison combined prevent bias or systematic favoritism.

A footrace longer than the $26.2$ miles of a long-distance race is known as an ultra-long-distance race. After ultra-long-distance races, sprinters frequently get respiratory problems, thus scientists randomly assigned ultra-long-distance runners to receive either nutritional C or a placebo treatment. Stratified random samples are samples taken from different strata in a diverse population using simple random sampling. Because a sample from each group might be selected and then all of the selected groups would be equally represented in the chosen sample, the stratified random sample sampling method should be utilized.

Random assignment is mostly used to form groups and reduce bias in the final outcome. As a result, it would be used to eliminate prejudice and influence the outcome.

The placebo rate of $68$ percent is much greater than the vitamin rate of $33$ percent, implying that the observed difference is excessive.