ENVS278 Chapter Notes - Chapter 17: Ingot, Null Hypothesis, Standard Deviation
4 Oct 2016
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Manufacturing ingots which are large pieces of metal used in airplanes and cars. If cracks are detected in the ingots during manufacturing they cannot be used and therefore must be recycled (very expensive), and therefore want to avoid cracking. Assuming changes haven"t happened so we will test them. Could be slightly different each time a sample is completed (think about how big the change has to be) In statistics, when considering how big the change must be we consider we naturally think of finding the standard deviation (so now find standard. Changed the process and 400 new ingots have been made; the sample size of. Sd( ) = 0. 02: since we know both parameters of the normal distribution model p. =0. 20 and sd( ) = 0. 02 we can now fund how likely it is to observe a rate of 17% using the zscore: z= (0. 17-0. 20)/0. 02, z= -1. 5.
