Recording and Tabulating Experimental Data

When recording data write your observations carefully, and completely. Do not use small scraps of paper. Label columns of data correctly and record ALL your results - nothing which is observed is 'wrong'. Only after careful assessment should a data point be discarded.

Label columns in tables and the axes of graphs by giving the physical quantity, followed by / and the appropriate units,

e.g.
	Length:	L / m
	Temperature:	T / K
	Surface area:	A / m2

Note:

• If the logarithm, square root, or some other function of a quantity is to represented, the units must appear within the argument e.g. ln[p/(Nm^-2)].
• In cases where the quantity to be plotted is an inverse, say the inverse of absolute temperature, the axes may be labelled 1/(T/K); a more elegant way of writing this is K/T.
• If very small or very large numbers are measured in an experiment, say times of 0 s, 500 s, 1000 s, 1500 s, ..., then writing all the zeros is time consuming and untidy. Instead the data should be presented as 0.0, 0.5, 1.0, 1.5 and labelled as 10^-3 t/s. This means that the figures on the axis are 10^-3 x the time in seconds. For example, if the number 0.5 is in a table with the column labelled 10⁴ t/s, then the actual value of this observation is 0.00005 s.

Important Note: Always give the units when quoting a result.

Significant Figures

It is pointless to quote a result to more significant figures than the precision of your measurement justifies. For example, if you are measuring a distance using a ruler then a result to the nearest mm is probably the best that can be achieved. (Note : Quote the error with the same number of decimal points as the measurement). Thus: L = (0.090 ± 0.001) m, not: L = (0.09 ± 0.001234) m

When you are citing the result of a calculation (with associated error) then the error should be stated (i.e. rounded) to a one or two significant figures and the value quoted to the same number of decimal places as the rounded error. For example, a temperature of 298.15 K with an associated error of ±0.678 K should be cited as   T = 298.2 ± 0.7 K   or   T = 298.15 ± 0.68 K. Similarly, an energy of 6789.0 J with associated error of ±23.45 J should be cited as    E = 6789 ± 23 J   or   E = 6790 ± 20 J.

It is recommended that a greater number of significant figures are used in any mathematical manipulation of your data, to avoid rounding errors, but remember that the final answer should be quoted to the appropriate level.