# What does this mean? (Dynamic forces in modelling)

#### davemk

##### New member
Hi, hopefully this is a simple question and easily answered.

I've been doing some reading on the subject of mathematical modelling and examples of modelling reports. In one report, the failings of the model are put down to "dynamic forces". I've taken this to mean that there are external factors affecting the dependant variable that are not contained within the model. Am I right?

Sorry, I know it's probably a stupid question but just wanted clarification!

Cheers.

Dave.

#### CaptainBlack

##### Well-known member
Hi, hopefully this is a simple question and easily answered.

I've been doing some reading on the subject of mathematical modelling and examples of modelling reports. In one report, the failings of the model are put down to "dynamic forces". I've taken this to mean that there are external factors affecting the dependant variable that are not contained within the model. Am I right?

Sorry, I know it's probably a stupid question but just wanted clarification!

Cheers.

Dave.
Without more information it is difficult to say, but one possibility is that the model is constructed using a quasi-static approximation (things change but slowly so that dynamic effects can be ignored). Then you would expect the model to diverge from reality/experiment due to the ignored dynamic factors (forces).

CB

#### davemk

##### New member
It was a study into causes of crime, using economic deprivation as an influence of crime (along with detection / conviction rates). It suggested that "neighbourhood effects" were a dynamic force affecting crime. As neighbourhood effects wasn't included in the analysis, I understood "dynamic forces" to mean influential factors that were not included in the analysis.

#### CaptainBlack

##### Well-known member
CB
It was a study into causes of crime, using economic deprivation as an influence of crime (along with detection / conviction rates). It suggested that "neighbourhood effects" were a dynamic force affecting crime. As neighbourhood effects wasn't included in the analysis, I understood "dynamic forces" to mean influential factors that were not included in the analysis.
Ignored factors seems plausible. Normally one would hope these are small, as otherwise it is not worth modelling without them