Question 1026006
The array of the 13 values are as follows:

10, 10, 11, 11, {{{highlight(11)}}}, {{{highlight(12)}}}, {{{highlight(13)}}}, 14, 15, {{{highlight(15)}}}, {{{highlight(16)}}}, 16, {{{highlight(17)}}}

Their corresponding ranks are 
1.5, 1.5, 4, 4, 4, 6, 7, 8, 9.5, 9.5, 11.5, 11.5, 13

(The highlighted boxed numbers are the values from Variety 1.)

The sum of corresponding ranks of the highlighted numbers is T = 4+ 6+7+9.5+11.5 + 13 = 51

==> {{{U = n[1]*n[2] + (n[1]*(n[1]+1))/2 - T = 6*7 +(6*7)/2 - 51 = 12}}}

Looking at the critical values table of the Mann-Whitney U with {{{n[1] = 6}}} and {{{n[2]=  7}}} and {{{alpha = 0.05}}}, the critical value would be 6.

Since U = 12 > 6, we conclude that there is significant difference between the two yields, and the two varieties of mushrooms do NOT produce the same yield.