University learnersInspect and classifyExample · 1 question · 2 min

Signal or Noise?

Compare twelve calibration runs and decide whether a visible excursion repeats enough to investigate as a signal.

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Calibration offset across twelve trials

Trial · Offset · µm

Offsets of twelve calibration runs in micrometres, with control limits from −1.0 to +1.0 µm. Runs 3, 4 and 5 lie at 1.4, 1.6 and 1.5. Run 7 is the single highest value at 1.8. All other runs stay between −0.2 and 0.3.

Show data as a table

Trial	Offset
1	0.2
2	0.1
3	1.4
4	1.6
5	1.5
6	0.3
7	1.8
8	0.2
9	-0.2
10	0
11	0.1
12	0.2

Choose one answer

The control limits are −1.0 to +1.0 µm. The rule says: three neighbouring runs beyond the same limit are a signal worth checking. Which observation meets that rule?

Run 7: at 1.8 µm it is the largest excursion.Runs 3–5: three neighbouring runs above +1.0 µm.

Show a hint

Mark every value above +1.0 first. Then look for neighbours, not for the tallest point.

About this activity

What you practise: Separating a repeating pattern from a single spike with a clear decision rule.

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The control limits are −1.0 to +1.0 µm. The rule says: three neighbouring runs beyond the same limit are a signal worth checking. Which observation meets that rule? Offsets of twelve calibration runs in micrometres, with control limits from −1.0 to +1.0 µm. Runs 3, 4 and 5 lie at 1.4, 1.6 and 1.5. Run 7 is the single highest value at 1.8. All other runs stay between −0.2 and 0.3. Runs 3, 4 and 5 lie above +1.0 µm one after another – exactly the pattern the rule asks for. Run 7 is higher, but it is a single point between normal values. On its own it may be noise: note it and watch whether it repeats.