Data Collection, Storage & Testing
How Data Is Collected
Before an IT system can process or store data, that data must be collected. The spec divides collection methods into two categories. Primary data is gathered directly by the organisation: examples include sending an email survey, conducting an interview and publishing an online questionnaire. Primary data is current and specific to your needs, but it takes time and resources to collect.
Secondary data has already been collected by someone else — examples include books, government statistics, magazines and websites. Secondary data is often free and immediately available, but it may be out of date, biased or not exactly matched to what you need. In an exam scenario, you may need to judge which collection method suits the described context and justify your choice.
Primary data collection methods: email, interview, online questionnaire/survey. Secondary data sources: book, government statistics, magazine, website. Primary data is specific but costly to collect; secondary data is cheap and fast but may be outdated or not tailored to your needs.
Where Collected Data Is Stored
Once data is collected, it must be stored. The spec separates storage into logical location (where the data appears to the user) and physical location (where it actually lives).
Cloud storage is the key logical location: data is stored on remote servers managed by a third-party provider and accessed via the internet. Cloud storage is scalable and accessible from anywhere, but it requires an internet connection and raises data security and privacy concerns.
Physical storage splits into internal and external devices. Internal devices sit inside the computer: the primary hard drive stores the OS, applications and user files; a network drive is a storage device shared across a local network, allowing multiple users to save to a central location. External devices are removable and portable: a portable HDD (hard disk drive) offers large capacity at low cost but is vulnerable to physical damage; a portable SSD (solid-state drive) is faster, lighter and more durable but more expensive per gigabyte; a portable USB flash drive (memory stick) is small and convenient for small files; a network-attached storage (NAS) device connects to a network and provides shared storage without needing a server; a portable wireless drive creates its own Wi-Fi hotspot so multiple devices can connect without cables.
Exam questions often ask you to select a storage option for a given scenario. Think about: capacity (how much data?), portability (does it need to move between locations?), speed (how quickly does it need to be read/written?), cost and security (who else could access it?).
A photographer backing up thousands of RAW image files needs high capacity — a portable HDD or NAS device is suitable. A student saving a single coursework document needs portability — a USB flash drive works. A business with ten employees needing shared access to the same files benefits from cloud storage or a NAS device so everyone accesses the latest version from any device.
There are five named external storage devices: portable HDD, portable SSD, NAS device, portable USB flash drive and portable wireless drive. Each has different capacity, speed, cost and portability characteristics — always match your choice to the scenario’s needs.
Why Testing Matters
Testing is essential because IT products that have not been properly tested can crash, produce incorrect outputs or create security vulnerabilities. The consequences of not testing include data loss, financial damage, reputational harm and, in safety-critical systems (such as hospital equipment or traffic management), potential harm to people. The spec requires you to understand why testing is needed, the effects of not testing, and the advantages and disadvantages of testing.
Test Data
The spec identifies three types of test data. Valid test data is typical data the system should accept. Extreme test data is at the very edge of what is acceptable (e.g. 0 and 100 on a 0–100 scale) — it should be accepted. Invalid (erroneous) test data is data that should be rejected (e.g. −5 on a 0–100 scale, or the word “hello” in an age field).
A common mistake is treating extreme and invalid as the same. They are not: extreme values pass the check (they are valid, just at the boundary); invalid values fail the check. For example, on a ticket booking form where age must be 1–120: valid test data = 25; extreme = 1 and 120; invalid = 0, 121, “twelve”.
Technical testing checks that all functions work as specified — for example, that a formula produces the correct output, that navigation links go to the correct page, and that validation rules reject invalid entries. It is carried out by the developer.
User testing checks that real users can accomplish tasks effectively without confusion. It uncovers usability problems that technical testing misses — for example, a button may work technically but be placed in a position that users find confusing. Feedback from user testing is used to refine the HCI design and improve accessibility.