'internal assumption' is a correct and usable phrase in written English.
You can use it when you are referring to a conclusion one has come to based on their own thought process or thinking. For example, "I came to the internal assumption that the project was beyond my capabilities."
Ministers have been hit by leaks of previous internal assumptions and estimates made by outside bodies such as the Institute for Fiscal Studies.
"The Scheme" at Penguin Random House was designed to change external perceptions, but also to challenge internal assumptions about talent and what is "required" to work in publishing.
You have been exposed to regularly-used internal assumptions for your company.
An unexpected outcome is that the reduction in required profitability is independent of any specified risk cushion (NPV%) or long-term profitability (NPV); it is solely a function of background financial market rates and project internal timing assumptions vis-a-vis the enterprise' historic rate of return.
When reporting QI scores for use in surveys or internal activities, the assumption is that rates derived from assessment in the prior period reflect current status.
Since we can only refer to the input dataset itself, internal validation needs assumptions about a "good" structure of found clusters which are normally given by reference result in external validation.
Data were analyzed to examine data completeness, scaling assumptions, internal consistency properties, and factor structure.
Scaling assumptions, internal reliability, and internal construct validity were examined using available data from 1884 RA patients included in the Dutch Rheumatoid Arthritis Monitoring (DREAM) registry.
Based on data collected, the following psychometric properties of the ACTS were examined: acceptability (including data quality and targeting); scaling assumptions; internal consistency reliability and test-retest reproducibility; aspects of validity (including known groups and discriminant validity); and responsiveness.
It is shown that the resulting closed-loop system is well-posed and asymptotically stable under weak assumption on internal uncertainty and external disturbance.
