BIOSTAT LESSON 2 (copy)

Population

refers to the entire groups of individuals of interest under study

Target population

is the population from which representative information is desired and to which the influences will be made

Sampled population

population from which a sample will actually be drawn

Sampling

act of studying only a portion of population

Sampling

representative portion of the population is called sample

Sample

representative portion of the population is called

Reduce cost, increase speed, greater scope and greater accuracy

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

Sample size

n

Population size

N

Margin of error

0.05 or 5%

Slovins formula

n = N/(1+Ne²)

Z score

Z²

Margin of error

E²

Estimated proposition of the population

P

Cochrans formula

n=Z²x P x (1-P)/E²

Sample

must be selected so that it properly represents the population that is to be covered.

Reliability

the sample should give measures of the precision of the estimates

Practicable

third criterion that thee sampling design must be practical

Practicable

must be sufficiently simple and straightforward so that it can be carried out substantially as design

Efficient and Economical

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

Probability Sampling

was some form of random selection

Probability Sampling

it refers to a sampling method thatuses some form of randomselection.

Sample random sampling

simplest form of random sampling

Simple Random Sampling, Systemic Random Sampling, Stratified Random Sampling, Cluster Sampling and Multistage Sampling

Five Methods of Probability Sampling

Lottery Method, Table of random number, RAN function of a calculator, Software

Sample random Sampling

Lottery Method

this method is easy to carry outespecially if both population andsample are small, but can be tediousand time consuming for large population or large sample

Lottery method

most commonly used method in drawing sample

Lottery method

easy to carry out especially if born population and sample are small

Table of random number

sets of random digits arrange ij groups both horizontally and vertically

RAN function of a calculator

function in a scientific calculator that has the capacity to generate the random samples

Software

refers to any program used to generate random samples using computer

Systematic random sampling

method of probability sampling involves the selection of the desired sample in a list by arranging systematically or logically in either alphabetically arrangement or anyacceptable arrangement

K=N/n

Systematic random sampling formula

Sampling interval

K

Clusters sampling

when the population is very large and widely spread out over a wide range of geographical area

Stratified random sampling

divided into a number of non overlapping strata, so that the sample within a stratum are more or lesshomogeneous and samples among strataare heterogeneous

Multi stage sampling

sampling is done in stages

Multi stage sampling

the population is first divided into a number of first stage from which sample is drawn

Non probability sampling

does not involve random selection

Non probability sampling

refers to a sampling method whichdoes not involve random selection, the probabilities of selection arenot specified for each individual inthe population

Accidental/haphazard sampling

refers to non probability sampling method wherein the sample is selected by chance or availability

Judgemental/Purposive sampling

a non-probability sampling werein the sample are chosen based on experts opinion

Convenience sampling

wherein the samples are readily or easily accessible

Quota sampling

come up with or required number of sample no matter how they are selected

Snowball sampling

obtained by a way that an individual to be included was identifies by an individual who was previously included