Intro to Marketing Research: Sampling - Non-Probability Sampling, Convenience Judgment Quota Snowball Advantages/Disadvantages When to Use

What It Is

Non-Probability Sampling is a method of selecting a sample from a population where every member of the population does not have an equal chance of being selected. A classic example is the "Milgram Experiment" (1961) by Stanley Milgram, where participants were recruited through newspaper ads and social networks to participate in a study on obedience. This matters for marketing decision-making as it highlights the importance of considering the potential biases and limitations of non-probability sampling methods when making inferences about a population.

Key Terms & Concepts

• Convenience Sampling: A method where samples are selected based on ease of access or availability. Example: A researcher selects participants from their own social network.
• Judgment Sampling: A method where the researcher selects samples based on their own judgment or expertise. Example: A marketing researcher selects a sample of customers who have purchased a product online.
• Quota Sampling: A method where the researcher selects samples based on specific criteria, such as age, gender, or income level. Example: A researcher selects a sample of 100 customers who are between the ages of 25-45 and have a household income above $50,000.
• Snowball Sampling: A method where the researcher selects samples based on referrals from existing participants. Example: A researcher selects a sample of participants who have been referred by friends or family members.
• Non-Probability Sampling: A method where every member of the population does not have an equal chance of being selected. Example: A researcher selects a sample of customers who have responded to a survey online.
• Sampling Frame: The list of individuals or units from which the sample is selected. Example: A researcher uses a list of customers who have purchased a product online as the sampling frame.
• Sampling Error: The error that occurs when the sample is not representative of the population. Example: A researcher selects a sample of customers who are predominantly male, but the population is predominantly female.
• Bias: A systematic error that occurs when the sample is not representative of the population. Example: A researcher selects a sample of customers who are predominantly young, but the population is predominantly older.
• Generalizability: The ability to make inferences about the population based on the sample. Example: A researcher selects a sample of customers who are representative of the population, and the results can be generalized to the larger population.
• Sampling Size: The number of individuals or units in the sample. Example: A researcher selects a sample of 100 customers.
• Cronbach’s Alpha: A measure of internal consistency reliability. Example: A researcher uses Cronbach’s alpha to measure the reliability of a survey.
• Regression Equation: A statistical equation that predicts the value of a dependent variable based on one or more independent variables. Example: A researcher uses a regression equation to predict the likelihood of a customer purchasing a product based on their demographic characteristics.

Common Misunderstandings

• Misunderstanding: Non-Probability Sampling is always biased.
• Correction: Non-Probability Sampling can be biased, but it can also be used intentionally to select a sample that is representative of a specific population or subgroup. For example, a researcher may use Quota Sampling to select a sample of customers who are representative of a specific demographic group.
• Misunderstanding: Convenience Sampling is always the easiest method to use.
• Correction: While Convenience Sampling may be the easiest method to use, it is not always the most effective method. For example, a researcher may use Judgment Sampling to select a sample of customers who are experts in a particular field.
• Misunderstanding: Snowball Sampling is only used in social sciences research.
• Correction: Snowball Sampling can be used in any field where it is difficult to access a population, such as marketing research or public health research.

Quick Application / Identification

A marketing researcher is conducting a study on customer satisfaction with a new product. The researcher selects a sample of customers who have responded to a survey online. Which sampling method is being used?

Answer: Non-Probability Sampling (specifically, Online Sampling)

Explanation: The researcher is selecting a sample of customers who have responded to a survey online, which is a non-probability sampling method.

A marketing researcher is conducting a study on customer demographics. The researcher selects a sample of customers who are between the ages of 25-45 and have a household income above $50,000. Which sampling method is being used?

Answer: Quota Sampling

Explanation: The researcher is selecting a sample of customers who meet specific demographic criteria, which is a characteristic of Quota Sampling.

A marketing researcher is conducting a study on customer loyalty. The researcher selects a sample of customers who have been referred by friends or family members. Which sampling method is being used?

Answer: Snowball Sampling

Explanation: The researcher is selecting a sample of customers who have been referred by existing participants, which is a characteristic of Snowball Sampling.

Last-Minute Revision

• Non-Probability Sampling can lead to biased samples.
• Convenience Sampling is often used in exploratory research.
• Quota Sampling is used to select a sample that is representative of a specific demographic group.
• Snowball Sampling is often used in social sciences research.
• Sampling Size should be sufficient to ensure generalizability.
• Cronbach’s Alpha measures internal consistency reliability.
• Regression Equation is used to predict the value of a dependent variable.
• Sampling Frame is the list of individuals or units from which the sample is selected.
• Bias occurs when the sample is not representative of the population.
• Generalizability is the ability to make inferences about the population based on the sample.
• Sampling Error occurs when the sample is not representative of the population.
• Non-Probability Sampling is often used in marketing research.
• Judgment Sampling is used to select a sample based on the researcher’s expertise.
• Quota Sampling is used to select a sample that meets specific demographic criteria.
• Snowball Sampling is used to select a sample based on referrals from existing participants.