Types of Reliability in Research (With Tips to Measure Them)

By Indeed Editorial Team

Published June 10, 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Researchers are vital employees to various industries, as they help companies and organizations make advancements and appeal to customers. To conduct accurate research, these professionals often use assessments to determine if their methods are getting reliable results. Understanding the types of reliability in research can help you select the best method for your experiment and help ensure you are providing reliable results. In this article, we review the four types of reliability in research, share five tips on how to measure reliability within an experiment, and explore elements that can affect reliability levels within a test.

Types of reliability in research

Reliability in research refers to whether research methods can reproduce the same results multiple times. If your research methods can produce consistent results, then the methods are likely reliable and not influenced by external factors. Researchers can use the same procedures, instruments, indicators, and environment in each of their experiments to test reliability. This helps them replicate results, test the trustworthiness of the experiment, reject or confirm a hypothesis, reach conclusions, and support their theories. This reliability supports business products and services in all industries, because it allows companies to offer proof of what they claim their products can offer to their customers.

For example, before purchasing pills in a drugstore, you can check the instructions, active components, and side effects. All this information relies on trials and experiments that researchers conducted several times to confirm their findings and to offer trustworthy data to customers. Consistency in research may impact scientific, social, economic, and even political sectors. For instance, a political candidate who wants to launch a campaign may use studies completed on previous electoral events to prepare a strategy or perform preliminary polls. Researchers use different reliability measures depending on their objectives, including:

Re-test reliability

Re-test reliability, also known as stability reliability, is the practice of testing tools, procedures, and instruments several times during a given period. With this method, researchers usually employ the same subjects and instruments to conduct each new trial. They can compare their findings and look for any difference between the original experiment and subsequent tests. For example, a car manufacturer can test a new windshield model they want to install on all their car models. Before doing that, they conduct several trials to check the glass resistivity and compare their findings with the first test.

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Equivalency reliability

Equivalency reliability is the practice of conducting two experiments that aim to test two similar subjects. To do this, researchers may assess the outcomes of both trials and measure the correlation between them. To measure the degree of affinity, they can establish identical independent variables within both tests and observe if, by manipulating them, they obtain the same results in both trials.

For example, a teacher can prepare two math tests and change the figures on one of the tests. Then they can divide their students into two groups and let them take the tests. If the results are very similar, the teacher can affirm that there's a high level of equivalency reliability in the tests.

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Internal reliability

This practice comprises testing the reliability of an instrument by measuring skills or characteristics and then comparing the results to determine their degree of affinity. This type of practice usually involves a one-time test, as researchers want to avoid misleading the participants. Through this method, they can use a survey to measure variables such as customer satisfaction and test the effectiveness of the survey by comparing all the results.

For example, a company that has redesigned one of its stores may discover how female clients perceive the new look by conducting a poll among a group of women. The organization can then select a group of clients randomly that are visiting the store at noon on a specific Monday and also offer them the survey. If they obtain similar results, they can determine the correlation between the questions and the trustworthiness of the results.

Interobserver reliability

Interobserver reliability is the practice of using two observers to rate one event, product, or service. This method usually requires having two raters with similar work experience and educational and cultural backgrounds. Typically, the observers rate the event during or after conducting the observation process. This method looks for measuring the reliability of the results and the effectiveness of the instruments the raters are using. For example, two judges of a tv show who are rating the performance of a musician may deliver similar or identical verdicts, which means the trial's results have high levels of reliability.

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Tips to measure reliability within an experiment

Although reliability can assess the consistency of a specific measure over time, it may not fully validate a metric or method. The four types of reliability can offer different methods a researcher can use according to the nature of their experiment. Low levels of reliability can invalidate an instrument or the results, so it's beneficial to review all the data and variables before conducting an experiment. Here are some tips you can use to measure reliability in an experiment:

Set the experiment objective

The first step before starting an experiment is to set its primary objective, as this might affect the entire trial and indicate at the end of the process if you have achieved your goal. By setting the test purpose, you can better understand the value of the experiment, determine what instruments you may need, and what type of data you might be handling. This information can be essential to evaluate the convenience of the test you have planned and the equipment required.

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Choose the instrument and method

By selecting a type of reliability method, you can choose the type of experiment you want to conduct. This can help you choose the right instrument, as each method may allow and require different tools. For example, if you want to rank running shoes according to their traction, you may require the interobserver reliability method, which allows you to use a scale to rank the shoes.

Plan the experiment

It's beneficial to create a task list and an inventory to avoid missing an item, tool, data, notes, or person you may need. By planning, you can also understand all the implications and potential obstacles of the test. It can help you research and know if other investigations have used the method you selected in finding reliability. This can also help your team prepare and practise, which can benefit the real procedure.

Adjust your instruments

It's beneficial to create or modify your instruments depending on the type of person that's participating in the experiment. You can consider the participants' basic characteristics, such as age, gender, or language, but also you can evaluate other features like educational background, culture, or place of birth. For example, a car manufacturer that wants to assess how clients perceive its sedan models may prefer that 40-to-60-years-old individuals with a steady income answer its surveys.

Record all your observations

You can record on video and audio all the observations you've made during the experiment. The performance of the reliability method may depend on this, and by checking your recordings, you can modify, correct, and assess elements within the test. For example, while revising the videos of a focus group, you may notice that one participant isn't answering straightforwardly. This can allow you to substitute the person or talk with them, which might improve the test's reliability levels.

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Elements that can affect reliability within an experiment

Some tests can guarantee similar or identical results, which means that if a person takes a survey several times, they might obtain the same outcome. This can help researchers conduct successful trials and assess the reliability of the experiment. There are other factors they might consider during the investigation, including:

  • Physical or psychological states of the participants: It's important to ask the participant to maintain their focus on the activity.

  • Test length: An excessive number of questions may be distracting or lose the participants' attention.

  • Environmental elements: These factors refer to the natural weather conditions during the experiment or the office working environment.

  • Test clarity: By using simple and clear questions, researchers may help all participants understand the instruments.

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