Methods of analyzing scatter are described later in this lecture. Using these methods the value of a variable, say velocity , is reported as

Here is the mean value of , the uncertainty in the value of as determined from the scatter experiments and is usually expressed as a percentage. Confidence interval (CI) denotes the probability that a fresh experiment which determines produces a value between and .

A note of interest: Instruments of the earlier generation were limited by their least count . With substantial progress in science and technology, modern instruments can measure very small changes, say in resistance and voltage. Consequently, scatter in the experimental data arises from the influence of environmental factors on the flow field, rather than the measurement system itself.