The phrase "a collection of five studies" is correct and usable in written English.
You can use it when referring to a group of five separate research studies that are being discussed or analyzed together.
Example: "In this paper, we will review a collection of five studies that examine the effects of sleep on cognitive performance."
Alternatives: "a set of five studies" or "a group of five studies".
And a collection of three studies by Norad (the Norwegian aid agency) points out that if PbR is used when trying to persuade a government into doing something it doesn't want to do, we already know how unlikely that is to succeed from the whole aid conditionality experience (pdf).
Our focus group study is the fourth in a collection of four studies we conducted during e-prescribing implementation at The Everett Clinic.
Next, a collection of six case studies of sociotechnical systems in operation provides useful insights into the methods themselves as well as their associated advantages and disadvantages.
Of these, undoubtedly the most significant was the enormous Opus 39 collection of twelve studies in all the minor keys, which contains the Symphony for Solo Piano (numbers four, five, six and seven), and the Concerto for Solo Piano (numbers eight, nine and ten).
CONOR is a collection of ten different regional health studies conducted from 1994 to 2003 and from seven out of 19 counties in Norway.
In arguing for a more stringent approach to treatment, Torrey, who is also the executive director of the Stanley Medical Research Institute, which has a collection of five hundred and sixty-three brains used for studying the causes of severe mental illnesses, frequently cites research on the significance of anosognosia.
These were a part of a collection of fifty strains used in a recent study by Dekio et al. [ 13] in which the genetic diversity of P. acnes strains was reported against the genetic diversity and distribution of P. acnes strains from Japan and Europe using MLST.
In a previous study, two opposite genetically-based life-history strategies have been described from the study of a collection of twelve industrial strains of S. cerevisiae.
When St James started Study in 2009 with the Square Project, a collection of zero waste garments made using squares, it was intended to be more of a research project than a collection – hence the name of her line.
A collection of ten clade C envelope genes with diverse sequences was assembled for this study.
