The phrase "a marked variation" is correct and usable in written English.
It can be used to describe a noticeable or significant difference in something, such as data, behavior, or characteristics.
Example: "There was a marked variation in the test scores between the two groups of students."
Alternatives: "a significant difference" or "a distinct change".
5 More recent research has also identified a marked variation in generic prescribing by general practitioners (GPs; for data on statin prescriptions in England, see http://www.prescribinganalytics.com).com
Such a marked variation in the allele frequency spectrum is even more impressive in light of the strong linkage disequilibrium between the two exons in Europeans (see Additional File 2).
A marked variation in spectral properties with power density of excitation is also found, which has implications for assay design.
Some recent experiments have claimed a marked variation in the luminescence of cadmium selenide quantum dots conjugated to macromolecules linked to bacteria.
In particular, there is a marked variation in the stability regions obtained by simulating the multi-mode model and those obtained by taking averaged relaxation time of the modes.
There is also a marked variation by region, as shown by the second chart, but in every case there has been an increase of at least 50 per cent.
There was marked variation in trainees' A-level performance.
This erroneous concept and a need for evidence-based travel advice prompted a GeoSentinel study that demonstrated marked variation in morbidity rates for malaria, African tick bite fever, and other travel-related illnesses in persons returning from South Africa compared with persons returning from neighboring countries or other countries in sub-Saharan Africa (4 ).
For example, some Eucalyptus trees display marked variation in herbivore defence within a single canopy.
There were, however, a small number of people whose values showed marked variation across the measurement period.
This equates to a mean energy intake of 206 kJ/person/day, but marked variation by age exists (table 1).
