**2.6 Percentage uncertainties and error analysis**

In order to identify the accuracy and precision of the measuring tools and instruments used in this experiment work, this process error analysis was performed. Experimental errors occur due to conditions outside the experiment itself such as poor calibration of the instruments, observational errors, manufacturing errors, errors associated with experimental set-up and planning, besides environmental conditions existing during the experiment [33]. **Table 4** is a list of instruments, percentages of uncertainties of CO, CO2, UHC, NOX, exhaust gas temperature (EGT) and smoke opacity and percentage error analysis. These percentages of error analysis


#### **Table 4.**

*Shows measuring instruments, range of measurement, percentages accuracies and inaccuracies, as calculated from Eq. (2).*

*The Influence of Exhaust Gas Recirculation on Performance and Emission Characteristics… DOI: http://dx.doi.org/10.5772/intechopen.105011*

are derived from the root sum square method formula and expressed in equation form [1] as in Eq. (1).

$$R = \sqrt{\sum\_{i=1}^{n} X\_i^2} \tag{1}$$

Where R is the total uncertainty percentage, *Xi* is the individual uncertainty of all the calculated operating parameters, *n* is the total number of the parameters in the experiment and *i* is the ith term of the computed parameters. The total percentage of the uncertainty is thus calculated based on Eq. (2) as follows:

$$R = \sqrt{X\_1^2 + X\_2^2 + X\_3^2} + \dots \\ X\_i^2 \tag{2}$$
