[[ 0 1 2 3 4 5 6 7] [ 8 9 10 11 12 13 14 15] [16 17 18 19 20 21 22 23]] mean(axis=1)

The result of mean(axis=1) on the given array would be:

[ 3.5 11.5 19.5]

This calculates the mean value of each row, where axis=1 specifies that the operation should be performed along the second axis (i.e. the rows).