tailieunhanh - Engineering Statistics Handbook Episode 9 Part 11

Tham khảo tài liệu 'engineering statistics handbook episode 9 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Comparisons based on data from two processes The goal is In order to answer this question data on piston rings are collected for to determine each process. For example on a particular day data on the diameters of if the two ten piston rings from each process are measured over a one-hour time processes frame. are similar To determine if the two processes are similar we are interested in answering the following questions 1. Do the two processes produce piston rings with the same diameter 2. Do the two processes have similar variability in the diameters of the rings produced Unknown The second question assumes that one does not know the standard standard deviation of either process and therefore it must be estimated from the deviation data. This is usually the case and the tests in this section assume that the population standard deviations are unknown. Assumption The statistical methodology used . the specific test to be used to of a normal answer these two questions depends on the underlying distribution of distribution the measurements. The tests in this section assume that the data are normally distributed. NIST SEMATECH HOME TOOLS RAIDS SEARCH BACK NEXT http div898 handbook prc section3 2 of 2 5 1 2006 10 38 47 AM Basic statistics from the two processes The basic statistics for the test are the sample means and the sample standard deviations Form of the test statistic where the two processes do NOT have equivalent standard deviations If it cannot be assumed that the standard deviations from the two processes are equivalent the test statistic is The degrees of freedom are not known exactly but can be estimated using the Welch-Satterthwaite .