- Data
        - failure
        - suspension
        - interval

   - Distributions
        - Weibull (2 and 3 parameter)
        - Normal
        - LogNormal (2 and 3 parameter)

   - Parameter Estimation
        - Regression on X
        - Regression on Y
        - Maximum Likelihood

   - Confidence Intervals for parameter
        - Fisher Information Matrix
        - Likelihood Ratio (only in combination with
          Maximum Likelihood parameter Estimation)

   - Graphs
        - Q-Q-Plot
        - Threshold
             - adjusted for Threshold (Weibull or LogNormal)
             - not adjusted for Threshold (Weibull or LogNormal)
        - confidence bounds
             - on X
             - on Reliability
        - Contour Plot (Scale vs. Shape Parameter)
        - Failure Rate
        - Density

   - Options
        - Pre define parameter value(s)
        - Add table of descriptive statistics on chart sheet
        - Combine results of several data sets in one graph

Data  arrangement

   Single data set/variable

         Always arrange data as follows:
               Column 1: End Time (empty cells not allowed here)
               Column 2: Status (1 = failure or interval; 0 = suspension)
               Column 3: Count (# of data points that match Column1 and Column2)
               Column 4: Time of Last Inspection (for interval data only)

         The number of selected columns defines how ExStat interprets the data set:
               1 column selected:  data set contains failures only; no grouping (i.e. Count =1)
               2 columns selected: data set contains failures and suspensions; no grouping
               3 columns selected: data set contains failures and suspensions; with grouping
               4 columns selected: data set contains interval data

   Multiple data set/variables

         Multiple data sets are stored below each other in data sheet
                Column 1:     Group variable that identifies the data set/variable
                Column 2,...: Same as for single data set


   ExStat always groups data
      ExStat groups the information by each distinct failure/suspension value. Calculations are based on distinct values. The number of plotted data points (Q-Q-plot) equals
      the number of distinct failure values.

   Interval Data
      Interval midpoints will be used as failure values if the regression (on X or on Y) is used to estimate the parameters.


   most of the mathematics is nicely described in Reliasoft's Weibull++ manual

    failures only
         Q-Q plot ; 3 parameter Weibull                                data  charts  result1   result2   result3
         Q-Q plot adjusted; 3 parameter Weibull                            charts 
         3 parameter Weibull                                                failure rate      density    contour plot
    grouping , failures only ,   Q-Q plot                               data  charts
    grouping , suspensions, contour plot                            data  charts 
    grouping , suspensions, interval data , q-q plot             data  charts  result1  result2

    multiple variables in one chart                                     data  q-q  contour  summary  individuals