"likely effective" is a correct and usable phrase in written English.
It is typically used to describe something that is expected to be successful or have a positive impact. Example: Our new marketing strategy is likely effective in increasing sales.
Our three-drug combination is likely effective due to effects on multiple fronts.
Very likely, effective BSV has complex effects on parasite dynamics, and improved within-host models are needed to capture these.
Infusions with bactericidal effect (functional neutrophils and granules) was likely effective and responsible for the more rapid elimination of bacteria in susceptible mares.
Another important observation is that the combinations between drugs sharing similar therapeutic effects and star drugs are more likely effective combinations.
Other very annoying but likely effective methods to try include: Act like a 500-pound gorilla and jump on the furniture, while grabbing food from guests' hands during the insult shower.
Process measure of FAST tuberculosis infection control demonstrates delay in likely effective treatment.
Polarizing rhetoric rarely leads to good policymaking and focussing on hopeful, positive messages is likely more effective than continuing a cycle of denial and counter-denial.
However, Obama said during the 2008 presidential campaign that such a fence would not likely be effective.
He also predicted it would most likely "be effective in not just promoting awareness, but also facilitating action".
Empirically, our results indicate zoning and land acquisition are likely most effective when targeted to particular lakes.
But as far as smear campaigns, it is likely an effective strategy.
