Sit-Stand Option. Remand where hypothetical to vocational expert asked about jobs in which the claimant could "alternate position, sit or stand," and VE's did not state whether jobs listed were available on a part-time basis or could be performed while walking. The ALJ's report failed to clarify ambiguity in evidence of RFC. ALJ's assumptions about claimant's RFC was clearly not transmitted to the vocational expert. The hypothetical asked only about jobs in which the claimant could alternate position, sit or stand. For a vocational expert's answer to a hypothetical to be relevant, "the inputs into that hypothetical must correspond to conclusions that are supported by the outputs from the medical authorities." The ALJ must clarify the outputs by deciding what testimony will be credited and resolving ambiguities, and accurately transmit the clarified output to the expert in the form of assumptions.

Alternating Sitting and Standing. Claimant with ability to alternate between sitting and standing positions found to have sufficient residual functioning capacity for unskilled work. The need to alternate between sitting and standing does not preclude all sedentary work. SSR 83-12 provides that "unskilled jobs are particularly structured so that a person cannot ordinarily sit or stand at will." This does not mean that there are no sedentary unskilled jobs which allow a person to sit and stand at will.