"Error Variance When two measurements of an object are taken it is common for them not to be identical. These differences are caused by some errors which are sometimes unavoidable. Errors tend to make results misleading or inaccurate and may lead to nature being misinterpreted. There are two main sources of errors; random and systematic errors (Brereton). Under these there are other sources of error which include; environmental errors, equipment errors, procedural errors, and human error. Systematic errors are measurements that are usually dissimilar from the true value mostly due to the procedure or instrument used (Hogan) . Random errors are errors that occur due to chance either by slight changes in the instruments, the reading measurement method or the environment. Random errors are usually hard to be controlled or may be costly to control them while collecting measurements. Human error is usually mainly due to the limitations of the human abilities.  Factors that affect these sources of error are the; environment, operator (human), units being used in the test, method or procedure, calibration used, and equipment. These factors are supposed to be controlled if measurements taken are required to be precise and accurate (Brereton). Human error can be divided into estimation and transcriptional errors, estimation error occur when one is reading measurements from the instrument while transcriptional error when data is recorded in the wrong way.  Transcriptional errors occur for example when one is entering data and they miss a figure in the computer data sheet. An example of estimation error is when one person might read width as 2.3mm while another reads 2.2mm.  Equipment or instrumental error refers to the error obtained when an instrument is used inaccurately for instance using a calculator that rounds off figures incorrectly. The equipment can also have the incorrect calibration and units under test and these lead to errors. Environmental errors happen when factors of the environment interfere with measurements causing errors (Hogan) . For instance when you are measuring the weight of an object and there is wind which causes the scale to read inaccurate readings. Lastly procedural errors are recorded when different processes are used to determine the answers of same questions and the different procedures lead to the getting of different answers. For example if two individuals use different rounding and one rounds up while the other rounds down , they are bound to get different answers. References Brereton, Richard G. "Sources of error." Journal of Chemometrics, vol. 32, no. 9, 2018, p. e3017. Hogan, Richard. "6 Influences on Uncertainty in Measurement Results." Isobudgets, 1 July 2020, www.isobudgets.com/6-influences-on-uncertainty-in-measurement-results/. Accessed 28 Dec. 2020."