yes, it was
The only issue with the study is that the results are parsed out in a press release rather than in a peer-reviewed scientific article, showing all methods & details
synopsis:
2104 patients, either on ventilation or receiving supplemental oxygen, were given 6mg dexamethasone (oral or i.v.) daily for ten days.
Comparing them with 4321 patients on standard-of-care, the death rates definitely decreased with dexamethasone: the 28-day mortality for patients on ventilation with standard of care was 41%, and dex treatment decreased that to 27%.
For patients receiving supplemental oxygen, the 28-day mortality was 25%, which decreased to 20% with dex.
The 28-day mortality for patients who needed no respiratory intervention, the 28-day mortality was 13%, and dexamethasone had no effect on that whatsoever.
p-values and confidence intervals for the first 2 groups (on ventilation or receiving supplemental oxygen) were very good indeed, as one would hope from the large number of patients.
Summary here:
https://blogs.sciencemag.org/pipeline/archives/2020/06/17/dexamethasone-for-coronavirus-infection