From the PARcore Data Visualization Studio Landing Page, navigate to this report by selecting the DIF Item Curves report icon.   This report is only applicable for requests that include the Analysis Type of Item Analysis - Differential Item Functioning and at least one analysis had sufficient volume to run DIF.  If no analyses in the request had sufficient volume, this report will not appear on the Landing Page.


The bento box menu icon at the top left of the report can be used to navigate back to the Landing Page.
 




When first launching the report it will be empty.  Make initial filter selections in order to visualize the report.  Any filter with a red asterisk indicates it is required to have a selection made before the report can be displayed.


Filters
Refer to Visualize Results for general information about filter navigation for any report.  The filters for this report are:



 

• Analysis - select one comparison to view at a time.  
  • Upon first initializing this dashboard, the filter will display as "(Choose your analysis)" and a selection must be made. 
  • Select the search icon (magnifying glass) and enter search text to see Analysis filter options for the request you are viewing.  Using an asterisk in the search text box will display all possible analyses to choose from.  
  • Once the current analysis results have been reviewed, continue to use the search feature or utilize the slider arrows (< and >) to view each analysis one at a time.  If you only have one analysis to view, the slider arrows will be disabled.
  • The filter description will include the criterion score being analyzed as well as the reference and focal group.  Only one reference/focal group comparison will be displayed at a time.
  • If no comparisons within an analysis had sufficient volume to run DIF, that comparison will not be included in the filter list.  Only analyses with at least one comparison that met volume requirements will be listed.

• Refinement Type - select one refinement to view at a time.  
  • Upon first initializing this dashboard, the filter will display as "(Choose refinement type.)" and a selection must be made before any data is visualized.  Use the dropdown filter to display the possible refinements stored for this comparison group.  
  • The available refinement type(s) to choose from depend upon the user selected options for this analysis as well as the analysis results.  The available options are:
    • No Refinement:  This will appear if the user selected "No" to the analysis template option to Refine Criterion Score.  This will be the only refinement option available.
    • None Required:  This will appear if the user selected "Yes" to the analysis template option to Refine Criterion Score but the comparison analysis resulted in no C items and therefore no refinement was performed.  This will be the only refinement option available.
    • Before Refinement:  This will be available if the user selected "Yes" to the analysis template option to Refine Criterion Score and the comparison analysis resulted in at least one C item.  The dropdown menu should show both "Before Refinement" and "After Refinement" as options.  Selecting Before Refinement will display the frequency distributions and summary statistics before refinement was performed. 
    • After Refinement:  This will be available if the user selected "Yes" to the analysis template option to Refine Criterion Score and the comparison analysis resulted in at least one C item.  The dropdown menu should show both "Before Refinement" and "After Refinement" as options.  Selecting After Refinement will display the frequency distributions and summary statistics after criterion refinement was performed.

• DIF Flag:  This is a multi-select filter and allows users to select which items to display based on which flag(s) the item has.   
  • Upon first initializing this dashboard, the filter will display as (None) but should become populated once an Analysis filter selection is made. 
  • Default filter selection: (All)
  • Only flags that are present in the data for the analysis selected in the previous filter will be included in the dropdown menu.  
  • Selecting the blank entry will show items with no flags (A flags).
  • The dropdown list contains all possible combinations of DIF Category Flags and IS indicator that is present in the data for the selected analysis. Possible combinations that could be presented:
    • (All)
    • <blank value>    indicates an item with an A flag or no flag could be calculated
    • [IS]
    • B-
    • B- [IS]
    • B+
    • B+ [IS]
    • C-
    • C- [IS]
    • C+
    • C+ [IS]

       
              Example of DIF Flag filter selections
               


   

• Sort Order: Accession Number:   Users can select the item response curve to display, one item at a time, by selecting a specific accession number. 
  • Upon first initializing this dashboard, the filter will display as (Choose your accession number) and a selection must be made.  
  • Select the search icon (magnifying glass) and enter search text to see all accession numbers for the analysis you are viewing.  
    • Using an asterisk in the search text box will display all possible analyses to choose from.  
    • If you want to view a specific accession number, enter the accession number into the search text field.
  • The format of the displayed items is first by a sort order value, then a colon, then the accession number, a dash, then scoring version for that item.   
    • The sort order value is only meaningful in the data visualization tool and is used to ensure the accession numbers are being displayed in the preferred sort order, which is:
      • MST tests:  items are listed by ascending alphabetical assembly unit, then ascending sequence within each assembly unit.
      • PBT or IBT tests:  items are listed by ascending delivery order of the assembly unit, then ascending sequence within each assembly unit.
    • If your request processing options for Combined Item Responses the selection is 'Use Response for Accession # Within Specific Form/AU'  then the Assembly Unit ID is also included in the filter details after the scoring version number to better allow users to distinguish the item and assembly unit to select.
  • If an item has more than one scoring version there will be separate entries and therefore separate item statistics and graphs for each scoring version.  
  • Only accession numbers that appear in the analysis selected and with the item flags selected in the DIF Flag filter will appear in this list.  
  • Once the current item has been reviewed, continue to use the search feature or utilize the slider arrows (< and >) to view each item one at a time.
  • When moving to another analysis or if having change the item flag filter, you may need to make the accession number selection again before a report is displayed.  

• The top section of this report will contain header information that displays the DIF Flag(s), if relevant, and Item Type, as well as the sequence and assembly unit information for the item being displayed.  The assembly unit information is a concatenation of the assembly unit ID, assembly unit name, test measure, test measure type, and research usage type for that item.

• When hovering over the assembly unit information a tooltip will appear that also displays the full assembly unit information.  This tooltip is useful in cases where your assembly unit details are too long for the space allocated and become truncated.  In those cases, the tooltip display of the assembly unit information will display the full details without truncation.

• Separate curves display for each response (or credit-level when applicable) for the item. The standardized percent difference statistics for each response is displayed above the curve.   Each curve contains a reference group line (thin red line) and focal group line (thicker blue line).  
  • The Y-axis is Smoothed Proportion Choosing by default for all items.  
  • The X-axis is the Criterion Score (possible score range). 
  • A tooltip appears if you hover over or click on any plot point and contains the group (Reference or Focal), Y-axis value, and X-axis value for the selected data point. 

• The correct response(s), when applicable, will be marked with an asterisk.  If an item has no response-level statistics and only credit-level statistics then the credit level plots are displayed instead. 

• If desired, utilize the zoom feature to change the focus of the plot to get a closer view of a specific range of data points.  Refer to Visualize Results for general information about the zoom functionality for any report that contains plots. 

• When viewing an analysis that had refinement, a footnote at the bottom of the report will be included when viewing the refinement (Before or After) that is being stored to external services based on the "Statistics to use for external services" selection made by the user in the analysis template used for this request.

• Continue to use the Sort Order: Accession Number filter to navigate through each item you want to review.  If your report includes more than one analysis or comparison, use the Analysis filter navigation to move from one analysis to the next as you complete your review(s).