= Simple Random Sample = A '''simple random sample''' is a fundamental sampling design. <> ---- == Description == For a simple random sample, the probability of selection is equal across all cases. Most commonly, samples are taken without replacement, which is to say that a selected case cannot be reselected. For a SRS without replacement (SRSWOR), the probability of selection is given by: {{attachment:srswor.svg}} where ''N'' is the total count of cases, ''s'' is the sample, and ''n(s)'' is the sample size. In contexts where the sample size is a constant, it's often shortened to ''n''. A SRS with replacement (SRSWR) means that cases can be selected repeatedly. This requires the introduction of a 'distinct' case function, ''d(s)'', such that a summation over the sample is expressed as ''Σ,,i ∈ d(s),,''. The probability of selection is given by: {{attachment:srswr.svg}} ---- CategoryRicottone