What is the reliability?
Reliability refers to how consistently a method measures something. If the same result can be consistently achieved by using the same methods under the same circumstances, the measurement is considered reliable.
- You measure the temperature of a liquid sample several times under identical conditions. The thermometer displays the same temperature every time, so the results are reliable.
- A doctor uses a symptom questionnaire to diagnose a patient with a long-term medical condition. Several different doctors use the same questionnaire with the same patient but give different diagnoses. This indicates that the questionnaire has low reliability as a measure of the condition.
What is validity?
Validity refers to how accurately a method measures what it is intended to measure. If research has high validity, that means it produces results that correspond to real properties, characteristics, and variations in the physical or social world.
High reliability is one indicator that measurement is valid.
If a method is not reliable, it probably isn’t valid.
- If the thermometer shows different temperatures each time, even though you have carefully controlled conditions to ensure the sample’s temperature stays the same, the thermometer is probably malfunctioning, and therefore its measurements are not valid.
- If a symptom questionnaire results in a reliable diagnosis when answered at different times and with different doctors, this indicates that it has high validity as a measurement of the medical condition.
Ensuring validity
If you use scores or ratings to measure variations in something (such as psychological traits, levels of ability, or physical properties), your results must reflect the real variations as accurately as possible. Validity should be considered in the very earliest stages of your research when you decide how you will collect your data.
- Choose appropriate methods of measurement
Ensure that your method and measurement technique is high quality and targeted to measure exactly what you want to know. They should be thoroughly researched and based on existing knowledge.
For example, to collect data on a personality trait, you could use a standardized questionnaire that is considered reliable and valid. If you develop your own questionnaire, it should be based on established theory or findings of previous studies, and the questions should be carefully and precisely worded.
- Use appropriate sampling methods to select your subjects
To produce valid generalizable results, clearly define the population you are researching (e.g. people from a specific age range, geographical location, or profession). Ensure that you have enough participants and that they are representative of the population.
Ensuring reliability
Reliability should be considered throughout the data collection process. When you use a tool or technique to collect data, the results must be precise, stable, and reproducible.
- Apply your methods consistently
Plan your method carefully to make sure you carry out the same steps in the same way for each measurement. This is especially important if multiple researchers are involved.
For example, if you are conducting interviews or observations, clearly define how specific behaviors or responses will be counted, and make sure questions are phrased the same way each time.
- Standardize the conditions of your research
When you collect your data, keep the circumstances as consistent as possible to reduce the influence of external factors that might create variation in the results.
For example, in an experimental setup, make sure all participants are given the same information and tested under the same conditions.
Reference:
https://www.scribbr.com/methodology/reliability-vs-validity/
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