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Quiz yourself on Fieldwork Process and EnquiryGet your flashcardsBuild my revision planTrack my progress⚖️ Reliability, Validity, and Representativeness — Side by Side
| Concept | Key Question | Example of a Problem | Example of an Improvement |
|---|---|---|---|
| Reliability | "If I repeated this measurement, would I get the same result?" | Three students measure the same river width and get 3.2 m, 4.1 m, and 3.7 m — inconsistent technique | Take three repeat measurements at each site and calculate the mean; standardise who holds the tape and where it is anchored |
| Validity | "Does this data actually measure what I'm trying to measure?" | Using the number of cars parked in a street as a measure of deprivation — car ownership is linked to income but is not a direct measure of deprivation | Use multiple indicators of deprivation (e.g., house condition, garden maintenance, litter levels) and combine them into an index |
| Representativeness | "Does my sample fairly represent the whole population or area?" | Conducting a questionnaire only on Saturday lunchtime outside a shopping centre — this sample over-represents shoppers and weekend visitors | Use stratified sampling across different times of day and days of the week; vary the location within the study area |
Note: A dataset can be reliable but not valid (consistent measurements of the wrong thing), or valid but not reliable (correct measures that vary too much). The ideal is data that is both reliable AND valid AND representative.
Quick Check: Suggest two ways to improve the reliability of a river velocity investigation.
1. Take three repeat velocity measurements at each site and calculate the mean — this reduces the effect of random errors caused by turbulence, equipment misreading, or inconsistent technique. A single reading could be unrepresentative of typical flow conditions at that point in the channel. 2. Standardise the measurement method precisely: always measure at the same position across the channel (e.g., at the midpoint) and at the same proportional depth (0.6 × channel depth), ensuring the same person operates the flow meter at every site to eliminate variation in technique between observers.
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