I'm not a science student, and I had no idea what error bars were until I just googled them. I did take AP Chem in High School though, and in college I was a comp sci major before I switched to business. I got through all that without needing error bars, so it seems to me this is something only needed by math or hard science students? I am actually curious to know who needs this
Hi Shinji,
If you know what an "average" is, then you should know what 'error bars' are...even though it isn't taught usually, which is too bad! It's not difficult! When you find the average height, e.g., of a group of people, you should also ask: what's the average difference from the average? That is, how much, on average, do the people in this group differ from their group's average height? That's the "error" (an unfortunate name, mainly stuck for historical reasons).
Apple includes a sixth-grade science template, showing a bar graph comparing growth of plants with and without road salt: one bar shows the average growth with salt, the other bar shows average growth without salt.
This is good information. But: what if the growth of plants with salt was wildly variable - some plants did fine on road salt, while others grew very very slowly - and the non-road-salt plants all grew at about the same rate (were not highly variable)? This could be worth knowing!
The error bar shows this information. The salt plants will have a long "error bar" (a vertical line) attached to the graph showing their average height, meaning high variability, and the non-salt plants will have a short error bar. So you get both average and average-difference-from-average information in the same picture.
Or imagine, measuring heights of fourth grade boys and girls: maybe the boys are shorter than girls on average, but the variability is much higher, so some boys are much taller but some much shorter. (I have no idea if this is true, just made it up). This would be worth knowing, for business as well as science (if you're selling pants to fourth-graders, e.g.....)
So you can see how, any time you want to know an average measurement, you should also know what the so-called "error" is (which just means the average difference from the average, basically - technically there are various formulas - "standard deviation", "standard error" - but this is the idea).
The "standard deviation" - which is what I am talking about above - is actually given for the plant data by Apple, in the numbers sheet in the plant presestation template!
So hopefully Apple will put it in their basic spreadsheets as soon as possible, as a matter of improving public education
Hope this helped.