The experimental hypothesis for the Stroop investigation predicts that there will be a difference in the number of correct responses with age between the young and old groups of participants in the Stroop performance, the experimental hypothesis is bidirectional.

The analysis are as follows

U(N_old= 30; N_young= 30) = 300.500; z = -2.347; P = 0.019

How does the analysis above link back to the hypothesis being one-tailed or two-tailed?

Also, What does the type of inferential analysis (Mann-Whitney U) tell you about the data above - the normality and homogeneity of variance?