BIOSTATISTICS 3

Population

it refers to the entire group of people, animals, or things of interest in the study

Sampling

it is the process or method of selecting that sample

Sampling Population

selecting a smaller group of individuals (sample) from a larger group (population) that you want to study. researchers choose a sample that will represent the whole group for a study

Target Population

It is the group from which representative information is desired and to which inferences will be made.

Study/Sampling Population

is the population from which a sample is drawn

Elementary Units

The units in study population which cannot be divided further.

Stratum

A collection of elementary units

Sampling Unit

Refers to each member of the sampling frame. Sampling units may be individual animals (elementary units) or they may be aggregates such as herds, farms, or administrative regions

Sampling Frame

A list of members (all sampling units) of the study population

Sample Fraction

The ratio of sample size to study population size.

Sampling Error

Refers to the difference between the value being investigated, and the estimates of this value based on the different samples.

Objective of Sampling

to provide an unbiased estimate of the variable being measured in the population

Non-Probability Sampling

where not every member of the population has a chance to be selected. The researcher decides who will be included, so the selection is not random

Convenience Sampling

Judgement or purposive sampling

Accidental or Haphazard Sampling

Quota Sampling

Snowball Sampling

5 Non-Probability Sampling Methods

Convenience Sampling

Choosing people/items that are easiest to reach.

Judgement/Purposive Sampling

Choosing people/items based on the researcher's judgment or specific criteria

Accidental/Haphazard Sampling

Choosing whoever happens to be available

Quota Sampling

Data collectors are told to meet certain numbers (quotas) for groups.

Snowball Sampling

Used for "hidden populations" that are hard to find

Probability Sampling

where every member of the population has a chance of being selected. It involves the principle of randomization or chance

Simple Random Sampling

Stratified Sampling

Systematic Sampling

Cluster Sampling

4 probability sampling methods

Simple Random Sampling

Every person/item has the same chance to be chosen

Systematic Sampling

Choosing every "nth" person/item from a list

Stratified Sampling

Divide the group into smaller groups (strata) and pick randomly from each

Cluster Sampling

Divide the group into clusters, then pick whole clusters

Sample Size

the number of observations or individual data points selected from a larger population for a study, experiment, or survey.