The phrase "a substantial positive effect" is correct and usable in written English.
You can use it when discussing the impact or influence of something that is significant and beneficial.
Example: "The new policy has had a substantial positive effect on employee morale and productivity."
Alternatives: "a significant beneficial impact" or "a considerable positive influence."
Regression modeling indicates that factors related to streetscape enclosure have a substantial positive effect on perceived safety.
Our results suggest that co-administration of hADSCs and VEGF-C hydrogel has a substantial positive effect on lymphangiogenesis.
The researchers believe that the prudence exhibited by female directors in negotiating mergers and acquisitions has a substantial positive effect on maintaining firm value, and that this helps build the case for increasing the number of women on boards.
Moreover, publicity has a substantial positive effect: a ceremony increases stated contributions by as much as increasing the value of the award from $0 to $1000.
I prefer to think about climate change communication as a great opportunity for meteorologists to make a substantial positive effect on our world and expand the way we connect with our viewers.
We now know, for instance, that even brief mindfulness practice — typically, a kind of meditation that focusses on a particular aspect of the present moment, like your breath, your body, or a particular sensation — has a substantial positive effect on mental well-being and memory.
It says "being a recent immigrant or being of non-White British ethnicity has a very substantial positive effect on progress through school" as the children of immigrants typically have "high aspirations and ambitions, and place greater hopes in the education system than the locals do".
The Cafe boost is the headline, but many energy analysts believe that the renewable energy standard and the tax package will have a more substantial, positive effect on clean energy markets.
On the basis of updated evidence, a low dose of aspirin has no substantial positive effect on the likelihood of pregnancy and it should not be routinely recommended for women undergoing IVF.
Substantial positive effect of 10 nm AuNPs on a root hair growth was observed during root growth experiments (Fig. 4).
