AQA 7517 4.5.4.7: Range and precision
The free BugBot lessons that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
A fixed number of bits can only hold a fixed number of different values, but between any two real numbers there are infinitely many more. So most real numbers cannot be stored exactly. This lesson measures how wrong a stored value is, shows how the choice of format trades range against precision, and names what happens when a result is too big or too small to store at all.
- Rounding errors
- Absolute and relative errors
- Range and precision
- Overflow and underflow
- A real reading
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- A7.4 Errors, range and precision Data representation
Rounding errors, absolute and relative error, range against precision, overflow and underflow, with a real sensor reading. - A7.10 Project: a secure sensor packet Data representation
Pack a distance reading into fixed point bytes with flags and a checksum, encrypt it with a one-time pad and send it by radio.
Try it on a robot
The task from A7.4 Errors, range and precision, running here. Change the program and press Run.
The specification is AQA's own document; this page says which of our lessons teach point 4.5.4.7 and is not endorsed by the board.