## 2007-09-20

### Analysing scientific investigation

So you are here probably because you want to get a deeper meaning an concept of scientific investigation.

You should have probably been familiar with the steps involved in scientific investigation i.e. Identifying problem, making hypothesis, generating data etc...

However, what I would like to emphasis in this post is the different types of variable.

You should know that "A variable is a quantity that varies in value". It represents "something" that are involved in a measurement in scientific investigation. Thus, a proper scientific investigation always involve variables and its measurement. A quantity that can be measured is called a physical quantity.

Three types of variables are:

Manipulated variable is a variable that is set or fixed before and experiment is carried out. it is usually plotted on x- axis.

Responding variable is a variable that changes according to and dependent to manipulated variable. it is usually plotted on y-axis.

Fixed variable is fixed and unchanged throughout the experiment.

Now lets see how to make inference and hypothesis?

How to make inference and hypothesis?

Inference: state the relationship between two VISIBLE QUANTITIES in a diagram or picture.

Hypothesis: state the relation ship between two MEASURABLE VARIABLES that can be investigated in a lab.

How to tabulate data?

-the name or the symbols of the variables must be labelled with respective units.
-all measurements must be consistent with the sensitivity of the instruments used.
-all the calculated values must be correct.
-all the values must be consistent to the same number of decimal places.

A graph is considered well-plotted if it contains the following:

- a title to show the two variables and investigation.
- two axes labelled with correct variables and units
- scales must be chosen carefully and graph must occupy more than 50% of the graph paper.
- all the points are correctly drawn.
- the best line is drawn.