Experiments Focus on variables

Experiments Experiments are a way to try and find out the causes of things. Almost anything can be investigated with an experiment. Some of the greatest discoveries have come from experiments as these examples show. You will see they are mostly scientific as experiments are consider a scientific method. Eg.1 John Snow investigates a major outbreak of cholera in Soho in 1854. By plotting the address of sufferers on a map he is able to identify one particular water pump as the source of the disease changing the prevalent medical opinion of the time that Cholera was an air-borne disease and creating a viable method to combat the disease through improving the water supply. His discovery was guided by the fact that local monks, who only drank their home brewed beer and never water from the public supply, had not contracted cholera. Eg 2. Before Galileo’s time (1564 – 1642) it was Aristotle’s theory of gravity that was held to be correct, that heavier objects fall faster than lighter ones. However Galileo doubted this and was able to prove it with this elegant experiment. Dropping two iron balls one much heavier than the other he found that the two arrived at the ground at the same time. This discovery formed our modern understanding of gravity and spurred on a period of incredible development in scientific knowledge throughout Europe. - Eg. 3 Before William Harvey (1578 – 1657) the great medieval doctor Galen believed that blood flowed around the body according to a mysterious power known as “pnuema” and that the beating of the heart was coincidental. Harvey doubted this and began to experiment. He dissected a living snake and with a pair of tweezers pinched the main artery (vena cava) that carried blood to the snake’s heart. The heart lost colour, the snake seemed to suffer and deteriorate and behind the tweezers the blood accumulated and swelled in the artery. This simple experiment proved that blood flows uni-directionally around the body and that it is pumped by the heart.

Experiments and variables An experiment is simply a way of investigating the cause of something. The investigator changes one thing and records the effect it has. The thing that the investigator changes is the INDEPENDENT VARIABLE The thing that the investigator records is the DEPENDENT VARIABLE

Experiments and variables examples An experiment into how plants grow in light and dark environments The thing that the investigator changes is the INDEPENDENT VARIABLE aka IV The thing that the investigator records is the DEPENDENT VARIABLE aka DV

Experiments and variables examples An experiment into how time spent studying affects exam success The thing that the investigator changes is the INDEPENDENT VARIABLE aka IV The thing that the investigator records is the DEPENDENT VARIABLE aka DV

Experiments and variables examples An experiment into how exam success affects future earnings The thing that the investigator changes is the INDEPENDENT VARIABLE aka IV The thing that the investigator records is the DEPENDENT VARIABLE aka DV

Testing understanding Identify the IV and DV from the previous examples IV : DV:

Testing understanding Identify the IV and DV from the previous examples IV : DV:

Testing understanding Identify the IV and DV from the previous examples IV : DV: