| TranStats Frequently Asked Questions |
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How do I locate the data I need in TranStats? |
TranStats maintains data in data tables. Related data tables reside in the same database while databases are indexed by transportation modes, subjects and agencies that are data providers. To locate data, use whichever of the following methods that is easiest to you:
- Locate the databases within the category you work with.
Depending on your knowledge of the data, use one of the following methods:
- Under Data Library on the homepage, select a Mode, a Subject, or an Agency . All databases in the selected category will be displayed on a database page.
You can further narrow down the database list in the category by selecting a subject or mode from the filter box on that page.
- On the side bar, type in some content keyword(s), for example, freight or fatalities, and click Go. All databases with the keyword(s) in their content or fieldnames are listed in the database page.
- Select the database using the database short description available on the database page or click Profile to obtain more detailed description of the database.
- Click the database name to see all data tables within that database. Data tables listed under the same database are related to each other and their relationship is explained in the descriptions of these tables.
- Select the data table with the help of the short description on the data table page. To obtain more detailed information about the table, click Profile on the data table page.
If the data you are looking for happens to be under At a Glance or In Focus on the homepage, click more will lead you to the data. |
Can I bookmark the database or data table page? |
| TranStats interacts with a large database. As a rule, we do not recommend users bookmark any page except the homepage. Bookmarking the database or data table pages may work but the results are unpredictable. You should never bookmark any other pages you open after the data table page. |
When I click download for a table, there is a message on the top band indicating some restrictions. What are these restrictions and why do you implement them? |
| This message appears only when you have selected a very large table, one that has millions of records. TranStats does not provide the options of All time periods nor geographical areas. The restrictions ensure that you can download the selected data over the web within a reasonable amount of time. If you need complete data from these tables, contact TranStats customer service. We will either send you a CD or provide you with instructions to obtain the data via other means. |
How come the file I downloaded to my computer has an htm extension and when I double-click it, it opens in my web browser? How can I open my downloaded file in MS Excel? |
TranStats does its best to make sure that the file you downloaded has a csv extension and you can double-click it to open it in MS Excel. However, some older browsers do not support the specification of the files they download; they simply substitute the name with the web page name. To get the csv extension, the best way is to upgrade your browser to the latest version.
If you did get a file with the extension of csv but cannot open it in Excel by double-clicking it, you probably have an older version of Excel. In that case, you need to open the file using the Open dialog box in Excel (File > Open ) and specify the file as comma-delimited.
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I found it difficult to interpret some of the statistics I got. For example, what does the average (Avg) of population of a state mean? |
| TranStats provides some basic statistical analysis. For quick information, the tool is powerful. However, like all statistics tools, the interpretation of the numbers depends on the knowledge of the data and how calculation is performed. AVG in TranStats is the sum of values divided by the number of non-null records in the database. In the case you just cited, the answer lies in what each record in that data table represents. TranStats cannot and does not exclude combinations of filter selections that may not make sense. You have to make the decision of what filter selections to choose. |
Why is it that I cannot find Avg in Filter Statistics? |
| If you do not see Avg there, you probably see Proportion. The reason is TranStats supports analysis of two types of dependent variables: continuous and dichotomous. For continuous variables, such as dollar amount and ton-miles, you will see Sum, Avg, Min, and Max. Dichotomous variables are those that have values of 1 and 0 (yes and no). When such variables are used as dependent variable, TranStats provides Sum and Proportion. For a variable that indicates whether a flight is delayed, Sum counts the number of delayed flights while Proportion gives the percentage of flights delayed. As with other statistics, check the field description before interpreting what is presented in the table. |
How come I cannot select any variables when I have selected Count in the Filter Statistics box? |
| TranStats provides the Count statistic for counting records. That is why when you have selected Count, only *Records is available in the Filter Variables box. When you want to count the number of people, flights, or occurrences of some event, as a general rule, use Sum. |
What does the asterisk mean when in the Filter Variables box? |
| It marks a pseudo variable created for user convenience. *Records is one; *LoadFactor is another. These variables do not exist in the data table. TranStats creates them to help you carry out some useful computation often used in the industry. For example, Load Factor is the sum of passenger-miles divided by the sum of seat-miles, an indicator used in the industry. Such variables carry a user function and when you select it, the Filter Statistics box is unavailable and displays N/A. |
In some tables, I see "Unknown" or "Code Unknown" as code description. Why is it? |
| There are two situations you can see this code description: either the code itself is missing (NULL) or the data source does not provide a description for all the codes in that table. To interpret such codes, contact the data provider. BTS will continue to work with all agencies that provide data to improve data quality. |
Some tables do not have any fields for analysis. How come? |
There are several reasons that analysis can not be done on those tables:
- Survey data such as ATS -- weighted analysis will be available in the next release.
- Tables, such as FARS BAC, which contain imputed data -- not suitable for analysis.
- Tables, such as MSMS, which do not have enough information for analysis.
For these tables, TranStats does provide as much information as possible in database profiles, table profiles, and field lookup tables whenever available. |
How can I return to my table analysis from a map? |
| TranStats provides easy navigation to different types of analysis. Use the menu under Analysis Type to go to Table Analysis, Times Series, Crosstabs, Charts or Maps. As the current release offers mapping only for States and Counties, when you go to different analyses, the default category variable will be State Fips or County Fips. Use the Filter Categories to change the category for a new analysis if necessary. |
How does your map break up data? It seems that the bottom breakpoint of a group is the same as the top breakpoint of the next group. Is this correct? |
| Maps break data in quantile using equal distance. There is an additional group for null values (meaning no data available). The overlapping of the breakpoints are adopted to accommodate rounding. There is an implied > sign before the bottom breakpoint of the upper group and a <= sign before the top breakpoint of the lower group. |
Can I perform cut-and-paste on the results I produced in TranStats? |
| Yes, you can cut-and-paste the results from the table, its print version, or its search results. To achieve the correct alignment, paste the results into a table in MS Word or in an MS Excel spreadsheet. |
