Likely explanations for observing a statistically significant result in a study include

The observed effect size in your study was smaller than expected

Your positive study result was an error (Type I) due to randomness

Your study sample size was too small

Your study had more variability than expected

Your study had less variability than expected

Your study was poorly designed

You conducted too many hypothesis tests without adjusting for the many comparisons

Your study actually found a substantial effect

Your study sample size was too large

Choose all that apply.