Module 4 · Evidence-Based Diagnosis
4.1 What Each Instrument Establishes
8 min read
Practitioners accumulate instruments and then use whichever is nearest. A better habit is to decide, before picking anything up, which question you are trying to answer — because the tools divide cleanly into ones that find where to look and ones that establish what is there, and using the first kind as though it were the second is the origin of most bad damp reports.
Learning objectives
By the end of this lesson you will be able to:
- Classify each instrument as screening or establishing, and use it accordingly.
- Build a survey sequence that spends expensive methods where cheap ones pointed.
- State, for any reading you take, what claim it can support.
- Choose controls that make a reading interpretable.
Key terms
- Screening method
- Fast, non-destructive, comparative. Finds where a building differs from itself. Cannot establish a value or a mechanism.
- Establishing method
- Slower, usually destructive, quantitative. Produces a value or identifies a substance. Answers what is actually there.
- Control
- A reading taken in unaffected material of the same construction on the same visit. What makes any other reading interpretable.
- Survey sequence
- Screen the whole, sample the anomalies, test the hypotheses. Spending an establishing method where a screening method pointed.
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