Question one: Pick one of the

Question 1) :

Simple Random Sampling:-

Simple random sampling (SRS) is a method of selection of asample comprising of n number ofsampling units out of the population having N number of samplingunits such that every samplingunit has an equal chance of being chosen.The samples can be drawn in two possible ways. The sampling units are chosen without replacement in the sensethat the units once chosenare not placed back in the population . The sampling units are chosen with replacement in the sense thatthe chosen units areplaced back in the population.1. Simple random sampling without replacement (SRSWOR):SRSWOR is a method of selection of n units out of the N units oneby one such that at any stage ofselection, anyone of the remaining units have same chance of beingselected, i.e. 1/ . N2. Simple random sampling with replacement (SRSWR):SRSWR is a method of selection of n units out of the N units one byone such that at each stage ofselection each unit has equal chance of being selected, i.e., 1/ .N .Procedure of selection of a random sample:The procedure of selection of a random sample follows the followingsteps:1. Identify the N units in the population with the numbers 1 toN.2. Choose any random number arbitrarily in the random number tableand start readingnumbers.3. Choose the sampling unit whose serial number corresponds to therandom number drawnfrom the table of random numbers.4. In case of SRSWR, all the random numbers are accepted ever ifrepeated more than once.In case of SRSWOR, if any random number is repeated, then it isignored and morenumbers are drawn.Such process can be implemented throughprogramming and using the discrete uniform distribution.Any number between 1 and N can be generated from this distributionand corresponding unit can beselected into the sample by associating an index with each samplingunit. Many statistical softwareslike R, SAS, etc. have inbuilt functions for drawing a sample usingSRSWOR or SRSWR.

Question 2) :

The most obvious criticism about convenience sampling issampling bias and that the sample is not representative of theentire population. This may be the biggest disadvantage when usinga convenience sample because it leads to more problems andcriticisms. Systematic bias stems from sampling bias. This refersto a constant difference between the results from the sample andthe theoretical results from the entire population. It is not rarethat the results from a study that uses a convenience sample differsignificantly with the results from the entire population. Aconsequence of having systematic bias is obtaining skewedresults.

Another significant criticism about using a convenience sampleis the limitation in generalization and inference making about theentire population. Since the sample is not representative of thepopulation, the results of the study cannot speak for the entirepopulation. This results to a low external validity of thestudy.