There are two cognitive biases which might be called the positive outcome bias:

1.Publication bias -- the tendency for researchers to publish research which had a positive outcome. "Positive" in this sense means "eventful" as opposed to "uneventful".
2.Positive outcome bias (prediction) -- a bias in prediction in which people overestimate the probability of good things happening to them. Related to wishful thinking. "Positive" in this sense means "good" as opposed to "bad" feelings.