GRAPHS IN SCIENCE Bar Graph Line Graph Pie

GRAPHS IN SCIENCE Bar Graph, Line Graph, Pie Chart & Scattergram

Graphing is all about DECISIONS! Which sort of graph to draw? 1. 1. 2. 3. 4. Bar graph Line graph Pie chart Scattergram What are the variables for the X and for the Y axes? 2. 1. 2. Dependent variable – on Y axis Independent (manipulated) variable – on X axis What scale intervals to use? 3. 1. 2. X and Y axes can be different Do you need to start the scale from 0?

Advice • Use an HB (possibly H) pencil • Use a ruler • Plot points should be small x’s or • ’s • Plot lines are usually drawn straight with a ruler, from centre of plot to centre of plot • Do not use colours or pens until the end – for labelling and titles • Use a graph size and scales which fill the page but leave sufficient space for labelling

Bar Graph • A bar graph uses vertical or horizontal bars to display numerical information. • Bar graphs can be used to compare amounts. • Each bar is a discrete value – NOT related to any other bar • Choose an appropriate scale (with regular intervals). • The bars should have the same width. • Often bars are drawn in pairs or groups • Don’t colour in bars; rather, rule coloured bar lines

Line Graph • A line graph uses a series of plots to show changes in data over time or as some other variable changes • Plot a point for each data item, and then connect the plot points with straight lines.

Pie Chart • A Pie Chart is a graph of percentages where the entire circle represents the whole (100%). • Each wedge represents a percentage of the whole. • You might need to use a protractor.

Example: 10%, 40%, 50% Start with 50% = ½ Now look at 40% will be almost all of the top half. The remainder is labelled with 10%. 40% 10% 50%

Scattergram (Scatter Plot or Graph) • Plots the results from two variables – one on the X axis and one on the Y axis. • A scattergram is drawn to see whethere is a relationship (CORRELATION) between the two variables. • The corrleation may be shown with a TREND LINE. • Sometimes colour or shapes can be used to show a third variable.