(6 pts) 21.) In ME455 class (2017 Fall), students measured a time interval using
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(6 pts) 21.) In ME455 class (2017 Fall), students measured a time interval using their cell phone stop watch. The timer was set to to= 5 seconds and was measured five times. The data is collected and plotted in following figure. Each red star and blue bar represent the mean and standard deviation (STD) of one student. Twenty nine students attended the timing measurement activity. Statistics on the all data are shown in the left table in the figure. Compare each person's mean of the time measurement to 5 seconds (standard), we can apply calibration to the time measurement and have a random variable (T person-to) to represent calibration error. The mean and standard deviation of the calibration error are shown in right table. What are the random and systermatic anderrors, respectively? 5 Mean of all [s] STD of all [s] #Of all Mean of Calibration [s] STD of Calibration [s] # of Calib. 5.45 0.46 0.30 0.13 145 29 15 People Count 5 20 25 30 Random error: Systematic errorExplanation / Answer
Systematic error is a error that arise due to imperfect calibration, fault in the device and due to some other factors that effect all the participants. From the figure one can see that 18, 19, 20 and 21 participants are effected the most by this error. As the deviation from the true value is very large for these participants and deviation keep on decreasing like a trend. Hence it is considered as a best case of systmatic error.
On the other hand, random error is a error that occur in a random manner or fashion. It is not effected by other factors. For example, 7th participant deviation from mean is very high but it seems that it is not affected other facors like tools etc. It may happen that the participant may not to able to handle the instrument in a nice manner.
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