Stem And Leaf Plots

Stem-and-leaf plots are just like bar graphs turned sidewise and instead of the bars, the actual data is written. The stem is the part from which the leaf branches outwards.

Example One - Spray-on Skin Stemplot

Professor Fiona Wood, an Australian plastic surgeon, developed a remarkable healing process for burns victims. For first- and second-degree burns, she surgically removed a small section of the patient's own skin, added an enzyme to separate the skin cells, mixed them with a protective gel, and then sprayed it back onto the burn area. This procedure considerably reduced the healing time with far less scarring. The following data indicates healing time (in hours) of burns patients. Draw a stemplot of this data.

Healing time with spray-on skin treatment (hours)
100, 123, 120, 90, 95, 82, 119, 112, 115, 86, 122, 123, 128, 112, 116, 103, 117, 107, 108, 110

 STEM LEAF 8 2, 6 9 0, 5 10 0, 3, 7, 8 11 0, 2, 2, 3, 5, 6, 7, 8, 9 12 0, 2, 3, 3, 8

Did You Know That...?

The spray-on skin treatment has also been successfully used for the gravel burns of motorbike accident victims. According to the US National Highway Traffic Safety Administration, the chance of a fatal crash is 35 times more on a motorbike than in a car. The UK Department of Transport reports that motorcyclists have 16 times greater risk of serious injuries than when travelling by car.

Example Two - Back-to-Back for Spray-on Skin Stemplot

Draw a back-to-back stemplot to compare the healing times with and without the treatment.

Healing time without spray-on skin treatment (hours)
131, 147, 143, 158, 156, 152, 169, 167, 165, 163, 160, 144, 142, 156, 154, 168, 166, 165, 161, 160

 LEAF WITHOUT SPRAY-ON SKIN STEM LEAF WITH SPRAY-ON SKIN 8 2, 6 9 0, 5 10 0, 3, 7, 8 11 0, 2, 2, 3, 5, 6, 7, 8, 9 12 0, 2, 3, 3, 8 1 13 7, 4, 3, 2 14 8, 6, 6, 4, 2 15 9, 8, 7, 6, 5, 5, 3, 1, 0, 0 16

Question - Transplanted Organ Rejection Times

The simplicity of the spray-on skin method was that the patient's own skin cells were being used. When organs such as hearts are transplanted from a dead donor to the recipient patient, medication called cyclosporine must be given to reduce the possibility of the patient's immune system rejecting the "foreign" transplanted organ. The following data shows the rejection time (in months) of heart transplants. Draw a stemplot of this data. What do you notice?

Rejection time (years)
15, 11, 21, 12, 23, 13, 6, 25, 6, 37, 28, 17, 25, 16, 33, 4, 8, 2, 17, 5

Did You Know That...?

Regenerative medicine is a relatively new field where stem cells from a person's own bone marrow or umbilical cord blood are cultured (grown) into required cells (e.g. white blood cells to fight severe infection) or organs in a laboratory. These are then transplanted back into the same patient without rejection.

It is unethical and illegal for scientists to clone a whole human.