A transport analyst is investigating how the implementation of a new congestion charge in a city center affects average vehicular speeds.
The analyst has access to two sources of data:
Identify the correct statement regarding the classification and utility of these data sources.
Source 1 is primary data, allowing the analyst direct control over the measurement conditions, whereas Source 2 is secondary data, providing a vast historical baseline but carrying the risk of unknown data-cleaning or selection bias by the third party.
Source 1 is secondary data because it relies on automated physical sensors rather than manual tallies, whereas Source 2 is primary data because GPS tracking captures the exact, raw coordinates of the vehicles in real time.
Source 1 is primary data and is always preferred over Source 2, because secondary data from commercial databases is mathematically invalid for hypothesis testing due to the absence of a control group.
Source 1 is secondary data because the sampling period (4 weeks) is too short to represent the population, whereas Source 2 is primary data because the 5-year span is long enough to establish true population parameters.
235 exam-style questions on AQA A Level Psychology Data handling and analysis. Each one has a worked solution and a mark scheme showing where the marks go.