BIOSTATS CHAP 2.1

Population

refers to the entire group of individuals

target population

is a matter of subject

sampled population

statistical inference can be applied

sample

representative portion of the population

greater accuracy

reduce cost

greater scope

increase speed

four basic reasons for the use of samples

elementary units

the individual in the population on which a measurement is actually taken and made

sampling unit

the unit which are chosen in selecting the sample

sampling frame

a collection of sampling unit

representative of the population

sample must be selected so that it properly represents the whole population that is to be covered I.e. each individual must have a chance of being selected and this chance must not be zero

reliability

it should be possible to measure the reliability of the estimates made from the sample. in addition to the desired estimates of the characteristics of the population. the Sample should give measures of the precision of these estimates

practicable

the third criterion that the sampling design must be practical. it must be sufficiently simple and straightforward so that it can be carried out substantially as design.

efficient and economical

among the various sampling methods, one must naturally choose the method which to the best of our knowledge produces the most information at the smallest cost

sampling with replacement

the individual in the population may be chosen more than once in a sample

sampling with replacement

a selected individual is placed back into the population and could be chosen a second time

sampling without replacement

the chosen individual as one of the samples may no longer be allowed to be chosen again

sampling without replacement

an individual from a population can be selected only once