1. Copyright, Gerry Quinn & Mick Keough, 1998 Please do not copy or distribute this file without the authors’ permission Experimental Design & Analysis Presentation graphs

2. Bar graph top of bar represents single observation or mean x-axis categorical different bars for different groups

3. Bar graph Survey 5 Survey 4 Site Mean number of Cellana per quadrat Site Mean

4. Category or line plot each symbol represents single observation or mean x-axis categorical but quantitative lines often join plotting symbols

5. Multiple groups on scatterplots 020406080100 0 10 20 30 40 50 60 020406080100 0 10 20 30 40 50 60 % cover of Hormosira Number of Cellana Sorrento Cheviot Beach Sorrento Cheviot Beach

6. Depicting error or variability Plotting sample means Use an error bar for each mean Error bars can be: –standard deviation to indicate sample variability –standard error or confidence interval to indicate precision around mean Error bars are symmetrical and can be one sided or two sided

7. Error bars cbcpecpwrrsspfplb 0 10 20 30 40 Site Mean (+SE) number of Cellana per quadrat + 1 standard error

8. Error bars overlap each other and symbols

9. Largest and smallest error bar

10. Design of presentation graphics Make data stand out - avoid “chart-junk” Use visually prominent elements to show data Do not overlap graph elements –tick marks outside –use error bars carefully Avoid 3-d graphs for 2-d data

11. 0 5 10 15 20 25 1234567891 0 Cheviot Beach Sorrento Survey Mean number of limpets per quadrat symbols lie on axis tick marks overlap symbols legend clutters graph symbols too small line styles indistinguishable

12. 12345678910 0 5 15 20 25 30 Mean number of limpets per quadrat Survey Cheviot BeachSorrento “zero” marks indented tick marks outside legend outside frame clearly visible & distinguishable symbols & lines

13. Pie charts

14. Inappropriate 3-d graph Site spslbrrcbcpecpwfpe 0 5 10 15 20 25 30 Mean density of limpets