The phrase "a certain average" is correct and usable in written English.
It can be used when referring to a specific but unspecified average value in a context where the exact average is not defined.
Example: "In this study, we found that a certain average of participants preferred the new product over the old one."
Alternatives: "a specific average" or "an average value".
"And my grades had to be at a certain average to keep the car.
Judge John Gleeson said the settlements required only that Visa and MasterCard maintain a certain average discount.
Those rules relied mostly on mandates, like requiring automakers to have a certain average fuel efficiency across their entire fleet.
For a certain average contact pressure, not only can the real area of contact be determined by the newly developed statistical models, but also the average interfacial gap.
But a more satisfactory explanation is, that, when men live in society, a certain average of conduct, a sacrifice of individual peculiarities going beyond a certain point, is necessary to the general welfare.
If they successfully complete a program designed to prepare them for the university and maintain a certain average, they would be guaranteed a place at one of the university's campuses.
The semigroup representation (R :, widetilde{mathrm {H}}(W^s) rightarrow mathrm {End}(fancyscript {A}_V)) will be given by a certain averaging process involving the standard representation of the Heisenberg group.
For example, whereas an ethnic or racial group may have certain "average" traits--a shared faith, or certain cultural norms--the diversity within a group is usually larger than the differences between groups.
It also shows that for between-group comparisons (e.g., a comparison between the uptake of two probes), more subjects will probably be needed to be able to detect a certain absolute average difference between those groups, when the uptake is, on average, high compared to low.
The distributions are presented as the weight fraction of polymer chains of a certain number average contour length with a resolution (bin size) of 50 nm.
Wolff later chastised Williams, who made him a deal: the next time they met, if Williams had a certain batting average, he would do the show.
