Simple Random Sampling
It refers to the sampling technique whether each and every item of the population is described an equal chance of being included in the sample. Because selection of items in the sample depends entirely on chance, this method is called also chance representative or selection sampling.
This is assumed that if the sample is chosen at random and if the size of the sample is sufficiently large then it will represent all groups in the population
Random sampling is of two types as: sampling without replacement and sampling with replacement
Sampling is said to be with replacement while from a finite population a sampling unit is drawn observed and after that returned to the population before another unit is drawn. The population in this case continues the same and a sampling unit might be chosen more than once
If alternatively a sampling unit is chosen and not returned to the population after it has been observed the sampling is said to be without replacement.
Random samples may be chosen by the help of lottery method or table of random numbers or such as tippet's table of random numbers, fischer and Yates numbers or Kendall and Babington Smith numbers.