The phrase "a certain confidence in" is correct and usable in written English.
It can be used when expressing a level of trust or belief in someone or something.
Example: "She approached the project with a certain confidence in her abilities to lead the team effectively."
Alternatives: "a degree of trust in" or "some level of assurance in".
She liked the way he walked — there was a certain confidence in his gait.
You would think that such a request implied a certain confidence in the product's readiness for consumers.
"I suppose I have a certain confidence in my abilities now that I didn't have in my first one or two books.
And if you've played the game to Test level like we have, then you feel a certain confidence in your judgement, foreshortening or not.
In this short communication, ground-motion fields are simulated and receiver operating characteristic analysis is conducted to guide decisions on the number of sensors required to obtain a certain confidence in the rate of false alarms and missed detections.
The UK government's rescue package and the co-ordinated interest rate cuts around the world seem to have restored a certain confidence in banks, with shares in HBOS and RBS all up this morning.
What they mean is that success requires a certain confidence, a faith in oneself--and in that they are correct.
This seems to have engendered a certain confidence that is reflected in their subsequent careers.
The opportunities are endless for sponsored content, though it takes a certain confidence from the brand in the trustworthiness and reliability of a given influencer.
The PM's answering put-down, that if he had wanted Brexit on schedule, he should have voted for her deal, was delivered with a certain confidence, and she did seem in less faltering form today.
This vast experience in life lent him an aura of grandeur and dignity that expressed itself in a certain confidence about how the world works.
