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**Reflections on
the aspect of certitude in dendrochronological
dating**

A question frequently addressed to Dendrochronology is: How certain is a certified dating effectively? To answer this question we have to deal with the value figure for the mathematical degree of certainty which will be 99,99% under ideal conditions and which is published in every single dendrochronological report.

To put it completely: The probability of a samples synchronous position compared to a dendrochronological reference-curve is 99,99%. Thus, the formulation of the reverse conclusion would be: The chance of misinterpretation is 0,01 %. Considering all the standardized mathematical methods of dendrochronology, we have to be aware that in an interval of 10.000 years for instance, there may happen a random synchronicity in a certain dimension, which would indicate a false dating. The danger of misinterpretation is all the bigger the smaller the amount of available annual rings on a sample is.

Therefore, the customer should select the samples carefully, concerning especially samples with narrow and, therefore, often a maximum amount of annual rings. In order to avoid the risk of missinterpretation we strongly recommend to take at least an amount of 5-6 samples per archaeological feature or building phase into account. For synchronicities of a successful dating tend to back up each other, this improves the certainty of the datings, although this cannot be shown graphically in mathematical values. Therefore, archaeologists and building-researchers are in charge of an enhanced certainty of dendrochronological datings.

Detail of a tree grate. Oak (Quercus robur o. pretrea)

Sometimes building researchers or archaeologists
retain information about the timeframe the samples possibly could
date to. Any dating without information about the possible
timeframe suffers from a decreased ratio of certainty. On the other
hand,

if information is given by the customer, this would not affect
results in a prejudicing way. A dating for example can be
determined much easier if there are only two possible
synchronicities as if there are 10.000. All the bigger the interval
of time for a possible dating is, the more strict the criteria will
become for a acceptable dating result.

A scope of 10.000 years which a sample could possibly be dated to
needs a statistical degree of certainty of 99.99%. If values get
below this threshold, misinterpretation becomes increasingly
possible. Concerning the example of a dating within a range of
10.000 years, values < 99.9% would not be acceptable any more.
In a situation like that, this would be marked on the report. Thus
Archaeologists and building researchers can help dendrochronology
to enhance the certainty of datings by giving all information about
the possible timeframe.

To faciliate the interpretation of the results for building researchers and archaeologists, we emphasize the different stages of the mathematical certainty by coloured markings on the report. For this purpose we do use the following colour code:

Red = The sample does not meet the normative properties for dendrochronological dating. The given dating has to be regarded as questionable.

Yellow = Liability of the synchronous position is on the threshold.

Green = Good or even very good sample material. The given dating may be regarded as reliably backed.

**FR, Normandy:** A workshop for
carpenters at the Château de Gaillon, 25.05. -
02.06.2013

and some more Dendrodates for the
Normandy.

**NL, Schoonebeek - southern Drenthe
area:**

A systematical acquisition of the historical
building stock

**DE, Eastern Frisia - Romanesque
churches:**

Serial investigation of wooden
roofs

**NL, 's-Hertogenbosch:**

Is it possible to localize

historical town fires using
Dendrochronology?

**FR, Normandy:**

Renaissance of Granges after the Hundred Years'
War

**NL, Terborg:**

Archaeologists discovered a

big medieval settlement area

**RO, Central Romania:**

Enigmatic medieval carpentry