Which type of sample ensures that every individual has an equal chance of being selected?

The correct answer is a random sample, as this method is specifically designed to ensure that every individual in the population has an equal chance of being selected. This is fundamental to achieving a representative sample and minimizing selection bias, which can occur when certain individuals are more or less likely to be chosen.

In a random sampling process, each member of the population is assigned a number, and a selection process, often using random number generators or drawing lots, is applied to choose participants. This randomness enhances the validity and reliability of the research findings because it reflects the diversity of the population.

In contrast, convenience samples are based on ease of access and might not represent the population well, as they can introduce bias. Stratified samples involve dividing the population into subgroups and randomly sampling from those groups, which can sometimes lead to disproportionate representation if not done carefully. Quota samples involve selecting individuals based on specific characteristics to meet a predetermined quota, but this method does not guarantee that every individual has an equal chance of being selected, making it less random and potentially introducing selection bias.