A threshold position scan holds the raw readout signal fixed at 6, between calibrated endpoints 0 and 10, and moves only the decision threshold across three rows: threshold 3 reads the fixed signal as one, threshold 6 ties exactly and reads as repeat, and threshold 9 reads the same fixed signal as zero, exactly for the stated toy threshold rule. Real calibration has to choose this decision boundary carefully, since the same physical reading can be classified differently depending only on where the threshold was set.

A fixed raw signal reads as one, repeat, or zero depending only on where the decision threshold was calibrated. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The same raw signal can read as one

Chapter six scanned the signal at a fixed threshold. Here the signal stays fixed at 6 and only the threshold moves. With threshold 3, the fixed signal reads above it.

6>3⇒∣1⟩6>3\Rightarrow \lvert 1\rangle
Low threshold reads oneThe fixed signal sits above this low threshold.zero signal 0one signal 10threshold 3input 6 reads one

Threshold placement alone changes the verdict

The signal never changes across this scan. Only where the threshold was calibrated changes the result: below, on, or above the same fixed reading.

Tresult3one6repeat9zero\begin{array}{c|c}T&\text{result}\\3&\text{one}\\6&\text{repeat}\\9&\text{zero}\\\end{array}
Threshold on the signalThe middle threshold sits exactly on the fixed signal.zero signal 0one signal 10threshold 6input 6 reads repeat

A higher threshold reads the same signal as zero

With threshold 9, the same fixed signal now reads below it. Nothing about the measured signal changed; only the calibrated decision boundary did.

6<9⇒∣0⟩6<9\Rightarrow \lvert 0\rangle
High threshold reads zeroThe fixed signal now sits below this high threshold.zero signal 0one signal 10threshold 9input 6 reads zero