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DESPITE UTMOST CARE AND PRECAUTIONS AN EXPERIMENTER MAY TAKE TO ELIMINATE ALL POSSIBLE ERRORS, THE HAPPY GOAL IS SELDOM ATTAINED AND CERTAIN ERRORS ARE BOUND TO CREEP IN FOR EXAMPLE, EVEN IN AN APPARENTLY  SIMPLE MEASUREMENT OF FLOW VELOCITY WITH A PITOT TUBE ANY MISALIGNMENT OF THE PROBE, LEAKS IN THE PRESSURE TUBING, CHANGES IN THE BORE AND SURFACE CONDITIONS OF THE MANOMETER, ANY FLUCTUATIONS IN THE ATMOSPHERIC AND STREAM PRESSURE ARE LIKELY TO AFFECT THE PROBE READINGS AND GIVE RISE TO UNCERTAINTIES .ERRORS AND UNCERTAINTIES ARE INHERENT IN THE PROCESS OF MAKING ANY MEASUREMENT AND IN THE INSTRUMENT WITH WHICH THE MEASUREMENT ARE MADE. A STUDY OF ERROR IS IMPORTANT AS A STEP IN FINDING WAYS OF REDUCING THEM, AND ALSO AS MEANS OF ESTIMATING THE RELIABILITY OF FINAL RESULTS. THIS CHAPTER PROVIDES A BRIEF DISCUSSION ABOUT THE NATURE OF ERRORS AND STATISTICAL ACCURACY OF TEST RESULTS.

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