Compare the original table (partially completed):
Code:
table: Set A
+---+---+---+---+
| 1 | 2 | 3 | 4 |
+---+---+---+---+---+
| 1 | 0 | | 2 | |
+---+---+---+---+---+
Set B | 2 | | 0 | | |
+---+---+---+---+---+
| 3 | | 1 | | |
+---+---+---+---+---+
| 4 | | | | |
+---+---+---+---+---+
...with your table:
Code:
table: Set A
+---+---+---+---+
| 1 | 2 | 3 | 4 |
+---+---+---+---+---+
| 1 | 0 | 1 | 2 | 3 |
+---+---+---+---+---+
Set B | 2 |-1 | 0 | 1 | 2 |
+---+---+---+---+---+
| 3 |-2 |-1 | 0 | 1 |
+---+---+---+---+---+
| 4 |-3 |-2 | -1| 0 |
+---+---+---+---+---+
Note, in particular, the entry for Set A: 2 and Set B: 3, which was "1" (so the difference between Set A's value and Set B's value was taken in absolute value) and now is "-1" (so the difference was
not taken in absolute value). I suspect that all differences were meant to be taken in the same way; that is, all differences, despite the clear language to the contrary, are meant to be non-negative.
I will guess that you mean that you found sixteen entries in total, of which four had the value of zero. The probability, then, of obtaining a value of zero, on any fair draw (assuming replacement after all draws), is found by dividing the number of successes by the total number of results, or 4/16, which simplifies as 1/4 or, in the decimal, 0.25 = 25%.
P(difference not 2) = 14/16 = 7/8
correct?
Depends on how the table is
meant to be filled in!
By the way, you might want to mention this in your hand-on solution. That is, specifically state that the text of the exercise implies that some values must be negative, but the table implies that all values should be non-negative. Then maybe give "the answer" both ways, clearly stating which is which. And maybe raise the issue in class, because you're probably not the only student to be caught by this contradiction!
