Adding error bars to a bar graph in MS Excel 97
- Enter the means of the variable to be plotted in one column and the confidence interval half-width for each mean in another column.
- Click on the chart wizard icon (identified by a graph of coloured bars) or choose CHART on the INSERT toolbar.
Under CHART TYPE choose COLUMN and CLUSTERED COLUMN under CHART SUB-TYPE. Work through the windows adding titles for the x and y axes clicking on NEXT to move through the wizard prior to clicking on FINISH.
- Doubleclick on any bar in the resultant graph.
Click on the tab called Y ERROR BARS in the resultant FORMAT DATA SERIES Window.
Click on the display named BOTH and choose CUSTOM.
Highlight the standard error row in the spreadsheet. The co-ordinates of the standard error row should appear in the '+' box in the CUSTOM section.
Click on the window adjacent to '-' and highlight the standard error row. The co-ordinates of the standard error row should appear in the '-' box.
Click OK You should now have a bar chart with error bars. Doubleclicking on the error bars and clicking the PATTERNS tab in the FORMAT ERROR BARS window allows the user to change the style, colour or thickness of the lines forming the error bars.
A similar approach can be used for adding error bars to line plots of means for example, to illustrate 2-way interactions.
You can save confidence intervals and means in SPSS 12 or above for use for plotting in EXCEL using the output management system.
Mike Griffiths has put this MS Word guide together on producing a range of plots in EXCEL.