Tips & Tricks

WinSPC Helps You Determine if Your Data is Statistically Sound

Statistical Process Control (SPC) is a predictive science where seemingly random data is conditioned to behave more predictably. The distribution analyzer tool is a feature within WinSPC's Query Tool that is designed to help determine the best means of achieving that objective. Accessed from the Query Tool screen, it allows the user to observe the data represented in one of three typical modes, Individuals, X-bar and Median models, to determine if it can be mathematically modeled accurately. The user can also determine the validity of SPC for a characteristic's current data collection method.
There are four tabs in the distribution analyzer dialog box: Type, Distribution, Histogram and Probability Plot.

Type
This feature allows the user to observe behavior of the data when organized and represented in one of the three typical modes: Individuals, X-bar and Median models.



Distribution Tab

Select from three different System types, Classical, Johnson and Pearson, and choose a Distribution type to view where your distribution lies (displayed as a + symbol) in relation to other distribution types.



Histogram tab

This tab displays the sample data from the query with a superimposed curve representing the distribution specified on the Distribution tab.



Probability Plot tab

This tab shows where the relationship between the data and regression is the strongest and where it may be expected to deviate.



Access the Distribution Analyzer in WinSPC:
1. The Distribution Analyzer is located within the Query Tool screen. Access the Query Tool by selecting Query
from the Tools menu in the Administrator and Data Collection screens. You may also click the Query button
on the Data Collection tool bar.

2. In the Query Selector dialog box, choose a query book and click Open.

3. In the Query Tool, from the Options menu, select Distribution Analyzer. You may also access this feature
by clicking the associated icon on the Query Tool tool bar.