White94 Posted July 19, 2011 Report Share Posted July 19, 2011 Hey there guys,I have been working on my biology lab and am now just reviewing everything and making sure I have everything I need. It's been too long since I did one, and I neglected to brush up on my error bar skills before the end of IB1. On my graph my error bars stretch into negative values, even though none of my collected data is negative. Have I done something wrong here?Thank youWhite94 Reply Link to post Share on other sites More sharing options...
Keel Posted July 19, 2011 Report Share Posted July 19, 2011 Hey there guys,I have been working on my biology lab and am now just reviewing everything and making sure I have everything I need. It's been too long since I did one, and I neglected to brush up on my error bar skills before the end of IB1. On my graph my error bars stretch into negative values, even though none of my collected data is negative. Have I done something wrong here?Thank youWhite94Hi,There are two options for error bars. One is fixed values the other is % of the value. It sounds like your you have a fixed value error. Such a situation will only occur if you have an error greater than your value e.g. 2cm +/- 5 in which case you will have 0 to -3 covered by the error bar. Are you sure the values in are correct? Make sure to differentiate between % errors (e.g. 5cm +/- 20%) and absolute errors (e.g. 5cm +/- 0.5). 1 Reply Link to post Share on other sites More sharing options...
White94 Posted July 19, 2011 Author Report Share Posted July 19, 2011 (edited) Hey,Yeah what you said about fixed value error seems correct. I think I'm going to need to look again at the results. The biology coursework piece was based on two different forest types and the plant diversity within. The graph is based on average % cover of the different species in each forest. The standard deviation is then between the average % cover for each species present in both sites. I might have made a mistake, because %cover varies greatly between the two sites.Thank you Edited July 19, 2011 by White94 Reply Link to post Share on other sites More sharing options...
Rigel Posted July 19, 2011 Report Share Posted July 19, 2011 You can cut off the negative part of the error bar. 1 Reply Link to post Share on other sites More sharing options...
White94 Posted July 20, 2011 Author Report Share Posted July 20, 2011 My teachers have told me they have to be 1 standard deviation above and below :/ But it would look better...okay thank you Reply Link to post Share on other sites More sharing options...
Ezeh Posted July 20, 2011 Report Share Posted July 20, 2011 Instead of messing with the error bars, you can simply limit the x/y axis. If your x and y values cannot ever be below zero, then you can edit your axis to start at 0 1 Reply Link to post Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.