What is 'Population'

Population is the entire pool from which a statistical sample is drawn. In statistics, population may refer to people, objects, events, hospital visits, measurements, etc. A population can, therefore, be said to be an aggregate observation of subjects grouped together by a common feature.

BREAKING DOWN 'Population'

A population can be defined by any number of characteristics within a group, which statisticians use to draw conclusions about the subjects in a study. A population can be vague or specific. Examples of population defined vaguely include number of newborn babies in North America, total number of tech startups in Asia, average height of all CFA exam candidates in the world, mean weight of U.S. taxpayers and so on. Population can also be defined more specifically — number of newborn babies in North America with brown eyes, the number of startups in Asia that failed in less than three years, the average height of all female CFA exam candidates, mean weight of all U.S. taxpayers over 30 years of age, among others.

Most times, statisticians and researchers want to know the characteristics of every entity in a population, so as to draw the most precise conclusion possible. This is impossible most times, however, since population sets tend to be quite large. For example, if a company wanted to know whether each of its 50,000 customers serviced during the year were satisfied, it might be challenging, costly and impractical to call each of the clients on the phone to conduct a survey. Since the characteristics of every individual in a population cannot be measured due to constraints of time, resources and accessibility, a sample of the population is taken.

A sample is a random selection of members of a population. It is a smaller group drawn from the population that has the characteristics of the entire population. The observations and conclusions made against the sample data are attributed to the population. The information obtained from the statistical sample allows statisticians to develop hypotheses about the larger population. In statistical equations, population is usually denoted with an uppercase 'N' while the sample is usually denoted with a lowercase 'n.'

For example, let's say a denim apparel manufacturer wants to check the quality of the stitching on its blue jeans before shipping them off to retail stores. It is not cost effective to examine every single pair of blue jeans the manufacturer produces (the population). Instead, the manufacturer looks at just 50 pairs (a sample) to draw a conclusion about whether the entire population is likely to have been stitched correctly.

A parameter is data based on an entire population. Statistics such as averages and standard deviations, when taken from populations, are referred to as population parameters. The population mean and population standard deviation are represented by the Greek letters µ and σ, respectively. The standard deviation is the variation in the population inferred from the variation in the sample. When the standard deviation is divided by the square root of the number of observations in the sample, the result is referred to as the standard error of the mean. While a parameter is a characteristic of a population, a statistic is a characteristic of a sample. Inferential statistics enables you to make an educated guess about a population parameter based on a statistic computed from a sample randomly drawn from that population.

RELATED TERMS
  1. Sampling Distribution

    A sampling distribution is a probability distribution of a statistic ...
  2. Sampling Error

    A sampling error is a statistical error that occurs when an analyst ...
  3. Attribute Sampling

    Attribute sampling is a statistical method typically used in ...
  4. T Distribution

    A T distribution is a type of probability function that is appropriate ...
  5. Confidence Interval

    A confidence interval measures the probability that a population ...
  6. T-Test

    A t-test is an analysis framework used to determine the difference ...
Related Articles
  1. Investing

    How to Use Stratified Random Sampling

    Stratified random sampling is a technique best used with a sample population easily broken into distinct subgroups. Samples are then taken from each subgroup based on the ratio of the subgroup’s ...
  2. Insights

    These Companies Are Poised for Growth as Global Population Growth Comes Online

    While there are many concerns about population growth putting pressure on natural resources such as water and energy, these increased demands can spell profits for certain companies that can ...
  3. Insights

    4 Global Economic Issues of an Aging Population

    Discover why dramatic increases in life expectancy is creating significant socioeconomic challenges for many advanced industrialized nations.
  4. Investing

    How Demographic Trends Could Affect Your Portfolio

    See how trends in demographics like people's movements, ages, deaths and buying patterns affect business cycles and investment portfolios worldwide.
  5. Personal Finance

    China's Former One-Child Policy Explained

    A look at China's former plan to control population growth.
  6. Insights

    How Demographics Drive The Economy

    Demographics can have a profound effect on the economy. An aging population coupled with a declining birthrate points to a decline in economic growth.
  7. Insights

    What China's New Policy Means for Business

    Now that China has eliminated its one-child policy, how will the new policy impact businesses?
  8. Managing Wealth

    Americans Are Getting Richer...Kind Of

    Americans are getting richer – the number of affluent households is growing – but the rate is slower now than it was before the Great Recession.
  9. Investing

    Analysis: Motivating Factors Behind Pfizer’s Big Split

    Pfizer plans to split into three separate businesses in a major restructuring move. Here's what you need to know.
  10. Retirement

    The 10 Best Cities in Florida For Retirees

    The Sunshine State offers plenty of options for retirement-aged adults seeking warm weather and a favorable cost of living.
RELATED FAQS
  1. What are the disadvantages of using a simple random sample to approximate a larger ...

    Learn here what a simple random sample is, how researchers use it as a statistical tool and the disadvantages it carries ... Read Answer >>
  2. What are the advantages of using a simple random sample to study a larger population?

    Learn how simple random sampling works and what advantages it offers over other sampling methods when selecting a research ... Read Answer >>
  3. What's the difference between a representative sample and a random sample?

    Explore the differences between representative samples and random samples, and discover how they are often used in tandem ... Read Answer >>
  4. What is the difference between systematic sampling and cluster sampling?

    Learn about the differences between systematic sampling and cluster sampling, including how the samples are created for each ... Read Answer >>
  5. What is the difference between the standard error of the mean and standard deviation?

    Learn about the difference between the standard error of the mean and the standard deviation and how standard deviation is ... Read Answer >>
  6. How many multinational corporations operate in China?

    Discover the importance of emerging multinational corporations. As China's urban population grows, it will continue to be ... Read Answer >>
Trading Center