Statisical Analysis

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Statistical analysis

	State that error bars are a graphical representation of the variability of data.
	Calculate the mean and standard deviation of a set of values.
	State that the term standard deviation is used to summarize the spread of values around the mean, and that 68% of the values fall within one standard deviation of the mean.
	Explain how the standard deviation is useful for comparing the means and the spread of data between two or more samples.
	Deduce the significance of the difference between two sets of data using calculated values for t and the appropriate tables.
	Explain that the existence of a correlation does not establish that there is a causal relationship between two variables.

ACCURACY AND PRECISION

ACCURACY

Accuracy descibes the nearness of a measurement to the standard or true value, i.e., a highly accurate measuring device will provide measurements very close to the standard, true or known values.Example: in target shooting a high score indicates the nearness to the bull's eye and is a measure of the shooter's accuracy. Refer to pictures below:

PECISION

Precision is the degree to which several measurements provide answers very close to each other. It is an indicator of the scatter in the data.The lesser the scatter, higher the precision. The pictures given below clearly describe Accracy and Precision.

EXAMPLES

If we measure the length of a foot-ruler and get values of

12.01 in, 12.00 in, 11.99 in, 12.00 in.

These numbers are precise enough for us to believe that if we measure it again we would get 12.00+0.01 in. These measurements are precise but necessarily accurate. The foot-ruler may actually be metric ruler of 30.0 cm long. Our measurement is precise but not accurate.