Using the Scatter Plot to Analyze Bid Item Prices 

The Price Versus Quantity analysis tool enables you to compare prices for an item at different quantities based on an item bid history as defined by a bid history profile.

Accessing the Scatter Plot

There are five ways to access the interactive analysis tool. If you want to:

• Perform a quick analysis for a reference item, navigate to the Item Bid History component, enter values in the required fields, and then select Price vs Quantity Analysis from the Actions menu on the component header. The system displays the interactive analysis tool in a new browser window.

• Perform a quick analysis for a proposal item, navigate to the Price Proposal Items component. Expand the section row that contains the proposal item you want to analyze. Click the Actions menu on the proposal item row and select Open Scatter Plot.

• Perform a quick analysis for a cost estimate item, navigate to the Cost Estimate Summary component. Locate the item in the list, and click anywhere in the row to expand it. To the right of the Price field, click the Details button. In the Bid Based row, click the Price vs Quantity Analysis link.

• Perform a quick analysis for one or more cost estimate items, navigate to the cost estimate's Item Pricing Worksheet. Locate the item in the worksheet, and click the Details button to the right of the Unit Price field. In the Bid Based row, click the Price vs Quantity Analysis link.

• Perform an analysis for a cost estimate item and have the option to save your changes to the associated bid-based task, navigate to the Cost Estimate Item Bid Based Task Summary, and select Price vs Quantity Analysis from the Actions menu on the component header. The system displays the interactive analysis tool. After you modify settings and reprice, the Apply button becomes available, enabling you to save the changes to the bid-based task associated with the cost estimate item.

If you accessed the analysis tool from the Item Bid History component, the window displays the analysis based on the values from fields on the Item Bid History component. If you accessed the analysis tool from the Cost Estimate Item Bid Based Task Summary, the window displays the analysis based on the values from the concept, cost estimate item, and the bid-based task (for additional information about the calculations, see the Bid-Based Pricing Methodology Guide).

Different symbols are used for data points to indicate whether the point is included or excluded in the price calculation, and whether the inclusion or exclusion was determined by user selection on the plot or the model calculations. The following symbols are used for data points on the scatter plot:

Point to a data point to display a tooltip with the dollar amount and quantity of the item, and whether it is included or excluded in the modeled price. You can view additional information about a data point by clicking the Identify button and then clicking the point (see Identifying Data Points below).

Switching Between Regression and Average

To display the scatter plot with an average instead of a regression, select Average from the Actions menu on the component header. If an average is displayed because a regression could not be calculated using the settings in the selected profile, you can still use the analysis tool to calculate a regression. To display the scatter plot with a regression price instead of an average price, select Regression from the Actions menu on the component header.

Identifying Data Points

Pointing to a data point on the graph displays a tool tip with the dollar amount and quantity for the point. For bid history price points, the tool tip also indicates whether the point is excluded or included in the modeled price, and whether the point was excluded or included by the model calculation or by the user's selection on the plot. For the modeled price, the tool tip includes the count and variability.

To access additional information about a data point, click the Identify button, and then click the data point. The system displays an overlay with the following bid information:

For bid history price points, the overlay includes a Proposal and Vendor link. When you click the link, the overlay displays the proposal ID, description, and county. It also displays the bid vendor name, ID, bidding rank, and bid total. You can click the Pricing Info link to return to the pricing information overlay.

To exclude the data point from the calculation of the modeled price, click the Exclude link on the overlay. When you exclude the data point, the link changes to Include. For excluded data points, you can click the Include link to include the data point in the calculation of the modeled price. When you include the data point, the link changes to Exclude.

To close the overlay, click the Close button in the upper right corner of the overlay. You can continue clicking different data points to display identifying information about that point.

Using the Analysis Panels

You can change settings for the graph or the calculation by using the analysis panels on the right side of the analysis window. To expand an analysis panel, click the name of the panel you want to view, either Filter, Highlight, or Show (see Filtering Data, Highlighting Data, and Showing and Hiding Points and Lines below). You can switch between panels as needed. To collapse an expanded panel, click the Collapse button or the panel name.

Highlighting Data

The Highlight panel enables you to view values for Count, Price, and Variability for each data attribute. You can also apply a visual indicator to points on the graph that meet selected criteria. To expand the Highlight panel, click Highlight on the right edge of the analysis tool window. You can collapse the Highlight panel at any time by clicking the Collapse button.

To specify the variable you want to use to highlight data, select a value in the drop-down box at the top of the Highlight panel. The panel displays different attribute check boxes depending on your selection. For example, if you select Season from the drop-down menu, the panel displays check boxes for the seasons defined by your agency, but only if a data point captured by the analysis uses that value. For example, if your agency has defined Spring, Summer, Fall, and Winter as seasons, but the item you are pricing only has historical bid data for Spring and Summer, the system only displays check boxes for Spring and Summer.

To highlight data on the scatter plot, select a check box for the data attribute you want to highlight. To remove the highlighting, clear the check box.

For each check box, a row of data is displayed with values for Count, Price, and Variability. The price for each row of data is marked on the scatter plot by a short horizontal line at the same quantity as the modeled point. By default, the rows are displayed in descending order by price. You can click the Count, Price, or Variability links to sort the rows by that value.

About the Data

For in-depth information about how bid-based prices are calculated, refer to the Web-Based AASHTOWare Project Bid-Based Pricing Methodology Guide.