All 3 concepts compared against each other, the third concept does fulfil the most requirements. Some of the requirements were difficult to test definitively, since there was no opportunity to test the prototype with the walker and tricycle. The weight which the concepts are able to carry without failing for example, is difficult to estimate. Evaluating the attachment itself has similar difficulties. Instead, we would have to rely on intuition to assess requirements.
The selection was eventually decided upon through this comparison against requirements, which was in-line with the opinions of the group members and the co-designer.
This lead to the selection of concept 3. Shown below are some higher quality images that clarify the working of the design and the product.