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Who decides what is normal?

To look at us from the outside, it is clear that we are all different. We are also just as different on the inside. So how do you know if you are normal or not?

This can sometimes only be discovered when we get injured or develop an illness that requires medical attention. You might then need an X-ray, an MRI or other medical imaging technique that shows a picture of the inside of your body, or you might need surgery.

Deciding what is normal is usually based on statistics. A large group of people are tested, and normal is the result 95 percent of those people show. The number of people that are tested and who these people are will affect the results, so careful consideration needs to be given to these issues.

Nature of Science

When scientists are undertaking new research, they have to develop methods that ensure reliable data is collected. The data could be in many forms, including measurements and observations.

When researching new methods for detecting and diagnosing disease, it is important to be able to distinguish relatively accurately between normal variation and abnormal variation (due to disease).

Dr Eli Van Houten’s work on a method for screening for breast cancer only works if his team can screen out the natural variations between patients' breast tissue but pick up the variations in the tissue that could be a tumour.

They are using a method that will take pictures of the surface of the breast as it is moved. They are currently using silicon models, called phantoms, to test their method, rather than real breasts. When they take pictures of the surface of the phantoms as they move, they need to be able to tell the difference between a phantom with a hard lump in it and one without by looking at the difference in the surface motion. If the difference is not clear enough, they have to work out ways to improve their method so there is an obvious distinction between the normal and abnormal phantoms.

Dr Richard Watts’ work looking at damage to the brains of boxers requires a control group for comparison. A control group is a group that is the same as the group being studied, except in one aspect. In this case, the control group are males who don’t box of the same age as the boxers. Without having a control group, it would be hard to conclude if differences seen were just due to natural variation.

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