Negative results
The results of … were negative
We did not find …
There was little or no change in …
There was little improvement in …
There was little correlation between …
There was no detectable increase etc. in …
No effect of … on … was observed
… could not be identified
… was not significant
… remained constant
… did not increase the …
… did or does not significantly affect …
… was or were unaffected by …
… had little or no effect on …
the effect of … on … was minimal
… had little impact on …
… did not vary greatly with …
… did not change or alter etc. significantly
… showed no significant change in …
… is unlikely to have affected …
… is unlikely to have been affected by …
… was adversely affected by …
… was unsuccessful in …
We encountered a number of difficulties or problems
the failure of …
… failed to …
The results are somewhat distorted by …
only half of …
over half of …
Of a total of …, only …
… where information was available …
… for whom information was available …
Individual results vary; however, …
The experiments yielded conflicting data on …