You could use slight: ...consider the probability to be slighthttps://www.oxforddictionaries.com/definition...slight
Small in degree; inconsiderable: a slight increase; a slight ankle injury; the chance of success is very slight
More example sentences
In virtually every case, however, the degree of degradation was slight enough to be inconsequential.
Five of six genes, regardless of X or autosomal location, are increased in expression to a slight degree in mutant females.
Now that mightn't be just be in number of cases, it might just be in slight increases in margin return over time.
small, modest, little, tiny, minute, inappreciable, imperceptible, infinitesimal, hardly worth mentioning, negligible