Glossary

Evidence Log

By Jason Aiginitis17 Oct 2026

An evidence log is a dated index linking claims about progress to the records that support or challenge them. Each entry identifies the observation, source, relevant period and limits of interpretation. In mentoring, the log makes it possible to check a progress claim without rereading every session or searching multiple tools.

Why an evidence log matters

Session notes describe a conversation; an evidence log points to material that can substantiate what happened afterwards. A note saying that a pricing test was discussed is not evidence that the test ran. A dated experiment record may show execution, while sales data is needed to examine the result.

Evidence and interpretation belong in separate fields. The UK government's 2026 Magenta Book methods annex describes contribution analysis as testing an explanation against evidence and other influences. An independent mentor's log is not a formal impact evaluation, but it can preserve the material needed to challenge a convenient explanation.

How it works in practice

Assign each entry an identifier and link it to the relevant goal in client progress tracking. Save the source date and reporting period, not just the date you added the row. The example below is illustrative and records mixed evidence deliberately.

Field	Illustrative entry E-014
Claim being checked	The new qualification rule reduced unsuitable enquiries
Observation	12 of 40 enquiries were unsuitable, compared with 20 of 40 previously
Source and period	CRM export, 2026-09-01 to 2026-09-30; previous calendar month
Linked action	Qualification rule introduced on 2026-09-01
Limitation	Advertising targeting also changed; samples are small
Interpretation	Lower unsuitable share observed; mentoring contribution not isolated
Next decision	Continue monitoring with unchanged qualification criteria

Retain contradictory observations, missing data and corrections. If a dashboard is live, keep an appropriately secured dated extract or describe how the same report can be reconstructed. A source link is useful only while its evidence remains inspectable. Do not collect unnecessary personal detail just to make the record look complete.

At review time, select the relevant entries for a value recap, including unresolved limits. The guide to measuring coaching outcomes explains how to separate observed change from a claim about what caused it.

Common mistakes

Saving screenshots with no date range, filter settings or indication of which client they describe.
Recording only favourable observations and omitting results that weaken the proposed explanation.
Replacing an incorrect entry without preserving the correction and its reason.
Using a client quote as confirmation of financial impact when it expresses satisfaction instead.

Frequently Asked Questions

What should an evidence log contain?

Record the claim, observation, source, date range, linked goal and limitations. Add the interpretation and resulting decision separately so another reader can challenge the reasoning.

Is an evidence log the same as a progress report?

No. An evidence log is the underlying index of records, while a progress report selects and explains the relevant findings for a review. The report should remain traceable to that index.

Does an evidence log prove mentoring return on investment?

No. An evidence log organises supporting and contradictory material; it does not isolate causation or assign a monetary value. A return-on-investment estimate needs an additional cost model and explicit attribution assumptions.