Population vs Sample population vs sample

Population vs Sample

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The difference between Population and Sample

A sample is a subset (smaller group) of a population or target population. Every study has an inquiry and in order to answer it, a sample of a population is taken and studied. The sample is meant to be representative of the population and is meant to derive insights on the population as a whole. Samples need to be used because oftentimes it is extremely difficult, or impossible in some cases, to study a whole population.

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“Population” in Market Research

In research, population is defined as a whole set of elements that all qualify a standard parameter. In research, “population” doesn’t necessarily refer to the human population, instead it refers to any parameter of data that possesses a common trait.

For example, it can be the total number of buildings in a city or the total number of shoe shops in an area.

“Sample” in Market Research

In research, a sample is defined as a subset of a population. This sample is meant to be generalizable to the population in a study so that researchers can make inferences on the behavior or characteristics of the whole population.

For example, if a study is aiming to understand the sugar consumption of American teenagers, only a sample of American teenagers will be studied rather than the whole American teenage population.

There are many different sampling techniques and researchers choose the one that is most suited to their study. This will depend on a number of factors such as the type of study, financial limitations, time limitations etc.

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Most common sampling techniques

Sampling techniques can be broadly classified into two categories:

  1. Échantillonnage probabiliste

This sampling technique chooses a sample based on the theory of probability, giving all elements of a target population an equal chance of being selected in the sample group. These are the main types of probability sampling techniques:

  1.       Échantillonnage aléatoire simple
  2. Échantillonnage aléatoire stratifié
  3. Cluster Sampling
  4. Échantillonnage systématique
  1. Non Probability Sampling

This sampling technique relies on researcher judgment or convenience in order to choose a sample group. These are the main types of non probability sampling techniques:

  1. Snowball Sampling
  2. Convenience Sampling
  3. Judgmental Sampling
  4. Échantillonnage par quotas

Why should you choose a sample from a given population?

  1. It is cost effective: All studies have certain financial limitations. Surveying an appropriate sample size is a cost-effective method of studying a population.
  2. It is efficient: When a sample is studied, instead of a whole population, it is a much quicker process and is more time efficient.
  3. It is practical: Most studies aim to make inferences about large populations. These populations are too large to collect data from each element within them. Samples are representative of these populations and provide a practical way of studying them.
  4. Can potentially be more accurate than a census: Due to inconsistencies in responses, or the non-response bias, a census of a whole population can’t always provide accurate information. Instead, carefully selected samples can provide more accurate inferences of the population.
  5. Can prove to be more representative of a population: some studies aim to study the relationship between certain groups of people. In these studies, sampling can produce more accurate data as only certain groups of people are surveyed.

Comparing Population Parameter and Sample Statistic

The measure that describes the whole population is known as a parameter. The measure that describes the sample is known as a statistic.

Hypothesis testing is used to estimate how much a sample statistic differs from the population parameter, and the difference between the two is known as “sampling error”. Sampling errors exist because no sample will be identical to the population.

The lower the sampling error is, the better, as researchers want the study’s findings to be generalizable to the whole population. An easy way of reducing sampling error is by increasing the sample size.

Key differences between Population and Sample

The following table outlines some key differences between population and sample:

 

Population

Sample

A whole set of elements that all qualify a standard parameter.

A subset of a population.

Surveys of whole populations do not have a margin of error, barring human inaccuracy.

Surveys of sample groups hold accurate results only after taking the margin of error into consideration.

The measurable characteristic of a population such as its standard deviation or mean is known as ‘parameter’. It is the measurable or numeric element that defines the system of a set.

The measurable characteristic of a sample is known as a “statistic”. It is the descriptive component of the sample that is found using sample proportion or sample mean.

 

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