1 For example, the disorder sickle cell anaemia is caused by a mutation in the gene that instructs the building of a protein called haemoglobin. 2  This causes the red blood cells to become an abnormal, rigid, sickle shape. 3  However, in African populations, having this mutation also protects against malaria.
Optimistic time - generally the shortest time in which the activity can be completed. It is common practice to specify optimistic times to be three standard deviations from the mean so that there is approximately a 1% chance that the activity will be completed within the optimistic time.
Share on Google Plus. The vocational guidelines for Social Security disability define work activity as medium, light, or sedentary. This is how these work activity levels are defined. 1  Sedentary work means that you are able to sit for up to 6 hours in an 8 hour day and lift up to 10 lbs. occasionally during a day.