To determine whether it is more likely that two individuals are full or half siblings, go to the second page of your DNA results report. Under the table, you will see two indices: Full Sibling Index and the Half Sibling Index.
If the Full Sibship Index is greater than the Half Sibship Index, then the individuals are more likely to be full siblings. Likewise, if the Half Sibship Index is greater than the Full Sibship Index, then the individuals are more likely to be half siblings.
To calculate how many times more likely one type of relationship is compared to the other (full vs. half), take the larger number and divide it by the smaller number.
In this example, if a sibling pair has a Full Sibship Index of 100 and a Half Sibship Index of 2, then they are 50 times more likely to be full siblings than half siblings.
Similarly, if a sibling pair has a Full Sibship Index of 1.5 and a Half Sibship Index of 20, then they are 13.33 times more likely to be half siblings than full siblings (20 ÷ 1.5 = 13.33).