Sampling and Sample Size

Sampling Technique or Sampling

the process of selecting a number of individuals for a study in such a way that the individuals represent the larger group from which they were selected

Aim in Sampling

to draw conclusion for the entire population after conducting a study on a sample taken from the same population

Sampling Unit

it is the individual element or entity that is selected for sampling from the population. it is the smallest unit from which data is collected

Sampling Frame

complete list or database of all the items or individuals in the population that you want to study. it’s like a checklist you use to pick out who or what will be part of your sample

Importance of Sampling

allows researchers to study a subset of the population while still obtaining meaningful insights

Steps in Sampling

1. Define the population (N) to be sampled

2. Determine the Sampling Frame

3. Identify the sampling to be used

4. Determine the sample size

Sampling Techniques

Probability and Non-Probability Sampling

Probability Sampling

• Unbiased

• Selection done at random

Non-Probability Sampling

• Biased

• based on researchers judgement/personal choice

Simple Random Sampling

• each member of the population has an equal chance of being selected

• unbiased sample

• representative

Stratified Sampling

• divide the population into groups using some characteristic

• select a few members from each group

Cluster Samoling

• aka: are sampling

• usually applied when the population is large

• population is divided into groups and randomly selecting groups

• members of groups have different characteristics

One-Stage Cluster Sampling

the entire population is divided into clusters and a random sample of these clusters are selected

Two-Stage Cluster Sampling

adds an additional layer of sampling

Multi-Stage Cluster Sampling

is an extension of two-stage sampling, involving multiple layers of stages of sampling

Systematic Sampling

every nth number from the population is included in the sample

Convenience Sampling

the process of including whoever happens to be available at the time

Purposive Sampling

the process whereby the researcher selects (hand-picked) a sample based on experience or knowledge of the group to be samples

Quota Sampling

researcher gathers data from individuals possessing identified characteristics and quotes

Sampling Error

• expected when using a sample

• occurs when you take a sample from the population rather than using the entire population

Margin Error

determines how much higher or lower than the population mean you are willing to let your sample mean to fall

Confidence Level or Risk Level

tell the researcher that if the population is repeatedly sampled, the average value if the population is repeatedly sampled, the average value of the attribute obtained by those samples is equal to the true population value