Year 10 Science Fair Testing Notes

Fair Science Testing Notes
A hypothesis proposes a possible cause and effect relationship between two variables. This involves selecting one variable and suggesting how this variable might influence other variables

An independent variable is the variable that is changing in the experiment. It is sometimes called the manipulated variable. There can only be one independent variable, as any more than one can lead to unfair results.

A Dependent Variable is the variable that is getting recorded, made by the changes of the independent variable.

A Controlled Variable is the variables that you must keep constant during the test, to ensure the fairness of the test.

EXAMPLE
An example is an experiment looking at the growth of trees in the Dark, in a dimly lit room and in the direct sun. The independent variable is the location of the trees. The dependent variable is the growth rate of the trees, how tall the tree is after a certain time. The controlled variables are the size of the beginning trees, type of trees.

Controlled Experiments involve conducting two similar experiments side by side. Only one of the experiments tests the independent variable. This allows the comparison to be made between the responses of the two groups. The results of changes in the independent variable can be identified as they should only occur in the experimental group and not in the control group. Experimental controls are different from controlled variables.

A Correlation suggests that two variables might be linked, but does not provide evidence that they are connected. For example, height and weight are linked as taller people are generally heavier than shorter people.
If two variables are said to be positively correlated, they increase or decrease together. For example, lung cancer and smoking are positively correlated.
If two variables are said to be negatively correlated, then it means that one goes up while the other one goes down. For example, amount of exercise and likelihood of heart failure are negatively correlated.

Features of an Experiment
When writing up an experiment, remember to thing about: * The Hypothesis * What the variables are (independent, dependent and controlled) * Experimental group and control group * Measuring and recording results * Possible errors that could occur in the experiment

What makes a good experiment?
Good experiments are accurate, reliable and valid.
Accuracy refers to how close measurements are to the true value.
Reliability means the same results are produced after an experiment is repeated exactly
Validity refers to making sure that the experiment is a fair test.

For an experiment to be considered valid, it must meet a certain criteria: 1. It measures what it says its measuring 2. The conclusion does not contain statements about things that haven’t been tested 3. All variables are kept controlled 4. The experiment is accurate and reliable