PURPOSE -the primary objective is the purpose
of the sample collection.whether there is a requirement of the
quantity or quality of the collected data.for example if you only need the number
of person residing in the colony this is quantitative data but if
you need the data like the income level,standard of
living,expenditure pattern,this is known as qualitative
data,therefore the purpose must be clear before undertaking any
sample size calculation.
SCOPE AND SIZE OF MARKET-sample should be
based on the market size.example-suppose the market size is
small then data of each and every consumer can be undertaken and
the result would be completely reliable,but if the market size is
too big to cover then the random sampling and cluster manner
approach could be under taken.
RELIABILITY-the sample size also depends upon
the concept that how much reliability is being accepted from the
obtained data.example if only estimation is needed
then the secondary data can be undertaken but if crucial decisions
are to be taken then new and recent data is needed to study the
changing preferences,trends so the level of reliability can be
increased.
AVAILABILITY OF RESOURCES-resources plays an
important role in the sampling process,for example if there is any agency
whether government or private which records the data based on a
particular pattern suppose hospitals records the data of patient
under medication.medical company can get the data by spending an
amount but efforts and time on self operation can be
avoided.
ACCEPTANCE OF DEVIATION- deviation is also an
aspect concern with sample size.this means how much difference is
acceptable from the actual data derived.example - a company wants to collect
the information concerned with the person earning $10000 per month
but it is desiring to accept the standard deviation of +500 &
-500 now if the collected sample contains data of having income
of $10400 and 9700 also,then the data would be
accepted.