An article in Microelectronics Reliability [“Advanced Electronic Prognostics through System Telemetry and Pattern Recognition Methods” (2007, Vol. 47(12), pp. 1865–1873)] presented an example of electronic prognostics (a technique to detect faults in order to decrease the system downtime and the number of unplanned repairs in high-reliability and high-availability systems). Voltage signals from enterprise servers were monitored over time. The measurements are provided in the following table.

a. Using all the data, compute trial control limits for individual observations and moving-range charts. Construct the chart and plot the data. Determine whether the process is in statistical control. If not, assume that assignable causes can be found to eliminate these samples and revise the control limits

b. Estimate the process mean and standard deviation for the in-control process.

c. The report in the article assumed that the signal is normally distributed with a mean of 1.5 V and a standard deviation of 0.02 V. Do your results in part (b) support this assumption?

Statistics 401 Notes Statistics is about collecting data, organizing it, summarization, and then analyzing it. Stats Collecting o Ex: Surveys Organization o Grouping the data using graphs or charts Summarization o Finding the average- median, mean, mode o (center and spread of data- Ex: Standard deviation) o The lesser spread of data (smaller range) = a more reliable source because it is more consistent. Ex: Data with outcomes of 30-70 (40 range) is MORE reliable than a range from 0-100 (100 range) o Population is the set of all units under study Population is represented by a sample of these units (random sample). Analyzing o Based on the sample drawn, you are able to make a conclusion about the population. Variable Numerical (Quantitative) is when the data is measurable or countable o Ex: weight, age, height Discrete: specific pattern that has specific values Continuous: data that varies over an interval (infinite amount of answer between an interval) Categorical (Qualitative) is when the data is NOT measurable o Ex: race or gender Q: How to tell which is numerical or categorical A: Finding the average must make sense. Ex: Finding the average weight makes sense because you can have an average weight of 100 lbs and that data can be used. Or, finding