"a weaker effect" is correct and usable in written English.
You can use it to describe a diminished or lessened effect or result, such as a decrease in a particular effect relative to a prior condition. For example, "The new drug had a weaker effect than the original medication."
"Blue seems a weaker effect than red, but blue skies, blue water are calm and positive, and so that effect makes sense too".
Accordingly, the positron suprathermality has a weaker effect on the existence domain of solitary structures.
Strong first order effects for all three variables were observed while the interactions of the variables had a weaker effect.
Thus, this result predicts a weaker effect of a recession at entry on subsequent wages for women than for men.
Our results indicate a strong online learning effect for n-gram and chunking models and a weaker effect for simple recurrent network models.
Meanwhile, microwave thawing had a weaker effect than water bath on the viscoelasticity, microstructure and thermo graphic characteristics of starch-based sauces [9].
At Ra = 104, heat transfer is more dominated by conduction and the addition of nanoparticles has a weaker effect on heat transfer augmentation.
According to this idea, during film viewing, local processing of the narrative may strongly guide eye movements, while global processing of the narrative may have a weaker effect.
We find that Rh has a weaker effect than Pt on hydrogen production (which is similar to the case where these metals are deposited on TiO2 anatase [12]).
Response surface plot showed that extraction temperature exhibited a weaker effect whereas extraction time represented a relatively significant effect on the flavonoids yield.
A weaker effect of particle size on their burn time is predicted for smaller particles, in qualitative agreement with recent experiments.
