The phrase "a first estimation" is correct and usable in written English.
It can be used when referring to an initial assessment or approximation of a value or situation before further analysis or refinement.
Example: "Based on the data we have, a first estimation of the project's cost is around $10,000."
Alternatives: "an initial estimate" or "a preliminary assessment".
In this paper we aimed to evaluate the global cost of chemotherapy in the early stages of breast cancer in order to provide health decision-makers with a first estimation and the opportunity to make the best use of available data for estimating the needs of antimitotics and trastuzumab in the country.
The predicted models gave a first estimation for design and assessment of newly built metro depots.
A theoretical model successfully provided a first estimation of the initial two CFCs.
Second is the use of incremental analysis, employed on the created database, to obtain a first estimation of discontinuity parameters.
In summary, our results indicate which mechanical parameters are essential to the good functioning of the avian ME and provide a first estimation of their values.
Different stages of succession of their fish assemblages were compared to give a first estimation of succession time for changes in fish communities caused by anthropogenic impact.
Use these values as starting points for a second estimation where the compound response (aSCR and eSCR ) is estimated from the first principal component of all event-related responses.
Hence, a second estimation is carried out by imposing a nullity restriction on this estimator, without affecting the value of the other estimators.
One can simply stick to the standard synthetic control method without cross-validation since it does not contain a second estimation step for which the predictor weights' uniqueness is crucial.
As a second estimation of exacerbation severity, the number of individual increased symptoms was counted up in a minor, major and total symptom count.
While "semi-quantitative" at best, this data is used to provide a third estimation method for S/G ratio of the lignin remaining in the cell wall.
