The phrase "a certain number of staff" is correct and usable in written English.
It can be used when referring to an unspecified quantity of employees or personnel within an organization.
Example: "The company has decided to hire a certain number of staff to handle the increased workload during the holiday season."
Alternatives: "a specific number of employees" or "an unspecified number of personnel."
We only have a certain number of staff trained and they aren't robots, they have to go home and sleep so that is a real challenge.
The hospital agreed with AT&T to sign up a certain number of staff members as wireless phone subscribers, in return for which AT&T put cellular antennas in its building.
As allowance is given to a certain number of staff, the department has to make adjustments.
For example, ensuring physicians feel that they are supported and perceive that they get what they need to effectively implement an innovation is more important than having a certain number of staff available or offering trainings in terms of encouraging implementation.
Unfortunately, 36 of these states waive said test when they're short on staff, leaving a certain number of students in the hands of educators who have not necessarily proven their ability to name the days of the week.
Adopting a corporate motto like "don't be evil" attracts a certain number of highly skilled, difficult-to-replace key staff who sign on because they don't want to be evil.
I am extremely thankful that I work in academia and that the last two colleges where I've been employed have had employee-assistance programs that permit a certain number of therapy sessions at no cost to their faculty and staff.
Currently, there is no national requirement for midwives or medical staff to perform a certain number of perineal repair procedures per annum to maintain their clinical competency.
But they make you hire a certain number of chicks, and they're always the least funny on the writing staff.
"They start out with a huge level of enthusiasm among teachers and staff, but it's really, really hard work, and after a certain number of years of 80-hour workweeks, the teachers get tired".
The results have been presented to the staff who, in working groups, gained awareness of possible effects of a certain number of working situations on their health.
