Though slump test is originally designed as a measure of workability, it turns out to be an indicator of excessive water content in concrete only.
Slump test is not considered as a measure of workability because:
(i) There is no connection between the test results of slump test and workability;
(ii) The test results exhibit large random variations which is greater than that due to observed differences in workability;
(iii) Concrete of different workability may have the same slump.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.