"a small but significant decrease" is correct and can be used in written English.
You can use it to describe a decrease in something that, although it may be small, still has an impact. Example: The company saw a small but significant decrease in profits this quarter.
We showed a small but significant decrease in fear.
Unlike previous randomized controlled trial, PEEP was adjusted with a PEEP-FIO2 table, whose consequence was a small but significant decrease in the PEEP level.
In contrast, AsPC-1 and MiaPaCa-2 xenografts caused a small but significant decrease in plasma thymidine concentration while the other three xenografts had no effect.
Students in the Lab group showed a small and marginally significant increase in the use of taxonomy and a small but significant decrease in their use of morphology.
There is preliminary evidence suggesting that the ICPI improves emotional function but not physical function, with a small but significant decrease in pain intensity and pain interference.
However, a small but significant decrease in R2 was found for control samples containing no ferrimagnetic material on raising the temperature from 1°C to 37°C.
Fenfluramine also produced a small but significant decrease in wheel running in ovariectomized rats that was not modulated by EB treatment.
We found a small but significant decrease in loss rate as distance from protected areas increased, supporting studies suggesting higher rates of landscape change near protected areas.
A second lumbar DXA evaluation performed in 38 patients after 1.00 ± 0.16 years confirmed a small but significant decrease of 1.6% per year in L2L4BMDvol.
Results show that (i) the proposed non-stationary variance model outperforms the stationary variance model, and (ii) a small but significant decrease of the rainfall prediction error variance is obtained with the optimised rain-gauge network.
