In which sampling method every member or item of the population has an equal chance of selection ?

Question

Accepted Answer

The correct option is 1:
Simple Random Sampling is the definitive answer because it is the most elementary and purest form of **probability sampling**, which is the class of sampling methods characterized by the principle of **equal and known probability of selection**. In this method, every single item or member of the population—the entire universe under study—is given an entirely equal chance of being included in the sample. This selection process is completely mechanical and unbiased, often achieved through lottery methods or random number generators. This inherent randomness ensures that the sample is highly representative of the population, thereby enabling the researcher to make statistically reliable inferences and generalisations about the larger population with a measurable level of confidence. It is considered the gold standard for avoiding selection bias.

The incorrect option is 2:
Judgement Sampling is incorrect because it is a non-probability method, meaning the selection of elements is **not** random. In this technique, the sample selection is based entirely on the researcher's informed personal belief or expert opinion about which population members are most appropriate and best suited for the study's objective. The selection is intentional and purposeful, thereby violating the fundamental rule that every member must have an equal chance of being chosen. This method is inherently susceptible to researcher bias and does not allow for the use of statistical tests requiring random selection.

The incorrect option is 3:
Quota Sampling is a non-probability method that involves dividing the population into subgroups (quotas) based on specific demographic characteristics (e.g., age, gender). Although the aim is to ensure the sample proportions match the population proportions for these characteristics, the actual selection of individuals to fill those quotas is left to the convenience or judgement of the interviewer. Since the final selection of who gets interviewed is subjective and non-random, all members of the population do not possess an equal chance of being included in the sample.

The incorrect option is 4:
Convenience Sampling is a non-probability method where a sample is chosen because it is easily accessible and convenient for the researcher to obtain. This means the selection is solely based on ease of access, proximity, or immediate availability, such as surveying people in a local shopping mall. Only those population members who happen to be readily reachable are selected, making the process highly non-random and introducing significant self-selection or positional bias, as the chance of selection is far from equal for all members.