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 …