The phrase "a subgroup of each" is correct and usable in written English.
It can be used in contexts discussing mathematical groups, set theory, or organizational structures where subsets are being referenced.
Example: "In our analysis, we found that a subgroup of each category exhibited distinct characteristics that warranted further investigation."
Alternatives: "a subset of each" or "a division of each".
Because it would be time and cost prohibitive to perform an extensive physical examination on all subjects in a trial this large, a subgroup of Soldiers from each company (n = 371) were randomized to receive additional testing in the form of a physical and ultrasound imaging (USI) examination of key trunk musculature.
Whole-genome RNA expression study was performed on a subgroup of four SCA28 patients, each carrying a different AFG3L2 mutation (p.Thr654Ile, p.Met666Val, p. Met666Thr, and p.Gly671Arg).
However, we did measure ionized magnesium and calcium in a subgroup of 40 patients in each group and found similar differences; moreover, these differences were statistically significant.
Levels of ionized magnesium and ionized calcium were measured in a subgroup of 40 patients in each group; these levels corresponded with the corrected levels of non-ionized electrolyte levels in these patients.
Only two 24-week phase III RCTs met inclusion criteria and could thus be included, and only a subgroup of the patients from each study was included, for the reasons discussed.
We also measured levels of ionized magnesium and ionized calcium in a subgroup of 40 patients in each group in order to determine whether the total serum levels of these electrolytes corresponded with levels of the ionized (i.e. active) form.
2. Narrative analysis of a subgroup of 30 transcripts (15 from each area) is being undertaken.
A subgroup of subjects was selected from each benzene exposure category as follows: 13 workers with very high exposure (> 10 ppm), 11 workers with high exposure (5 10 ppm), 30 workers with low exposure (< 1 ppm; average < 1 ppm), and 29 workers with very low exposure (<< 1 ppm; average < 1 ppm, with most individual measurements < 1 ppm) (Table 1).
Each of both obstacle courses was explained and demonstrated to a subgroup of 2 to 3 children and each child was evaluated and scored individually by one evaluator.
