Variables, tables and graphs

Things to consider before an experiment

Variables

Control group

What are the types of variables n its functions

Main types:

Independent variable (manipulated during an experiment to find out the AFFECT of the change)

Dependent variable (affected by independent variable, should be affected by only ONE independent variable and all other variables (control variables) which can affect this variable (dependent) are kept constant

Controlled/constant variable (kept the same throughout the test to ENSURE A FAIR TEST)

control groups functions

Serves as a standard for COMPARISON.

Subjected to the same experimental conditions as the experiment group, except for the variable being tested.

Tables, conditions

1 Framed, ruled in pencil

2 Large, well-planned to accommodate all data collected

3 Appropriate title written aboe

4 Table of results should include, in the heading of each column and/or row, the name of the measured or calculated quantity, together with the appropriate unit written after a slash

5 Each reading should be repeated, if possible, and average calculated

6 all readings and calculated average must be recorded in separate columns

7 The number of significant figures given for calculated quantities should be the same as the significant figures in the raw data used

8 A ratio should be calculated as a decimal number, to two or three significant figures (never give answer in fractions.)

9 Decrease in measurement should be indicated as negative values

10 The independent variable is always recorded in the first column of the table. The dependent variables will be recorded in subsequent columns

11 Do not show calculation inside the cells

12 In case of non-availability of data, one should write N.A. or indicate it by dash (-).

Graphs, types

Linear

Directly proportional

Rising curve

Falling curve

Curve that peaks at an optimal value

Curve that ‘plateaus’ to a constant value on the y-axis

Linear graph:

Best fit straight line

Directly proportional

A straight-line graph through the origin

Rising curve:

Dependent variable rises quickly at first, then more slowly

falling curve

dependent variable falls quickly at first, then more slowly

Curves that peaks at an optimal value

Curve that reaches its highest point due to a certain variable, hence indicating that variable is optimal for xxx

e.g.

enzyme activity peaks at a certain temperature, which hence is the optimum for that reaction

Curve that ‘plateaus’ to a constant value on the y axis

remains the same

e.g.

The rate of reaction remains the same even when substrate concentration increases after the point of saturation

graph conditions

1. title of graph to be written at the top to inform the readier about the variables investigated

2. clearly label the X and Y-axes.

3. include unit for measurement for variables (after a slash), if applicable.

4. The entire graph should be done in pencil, including all the labels and markings

5. Plot datapoints on the graph with a cross (x)