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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           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|EIA 
        Home > Transportation 
        Home Page > **Chapter 
        5. Detailed Tables**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|**Chapter 5. Detailed Tables**
      The following 
        tables present detailed characteristics of vehicles in the residential 
        sector. Data are from the 1994 Residential Transportation Energy Consumption 
        Survey.
      **Table Organization**
      The "Detailed Tables" section consists of three 
        types of tables: (1) Tables of totals such as number of vehicle-miles 
        traveled (VMT) or gallons consumed; (2) tables of per household statistics 
        such as VMT per household; and (3) tables of per-vehicle statistics, such 
        as vehicle fuel consumption per vehicle. The tables have been grouped 
        together by specific topics such as model-year data or family-income data 
        to facilitate finding related information. The Quick-Reference Guide to 
        the detailed tables indicates major topics of each table.
      **Quick-Reference Guide**
      **Topic and Table Number** 
      **Summary**
        Totals 
          - Table - 5.1
        Per Household 
          - Table - 5.2
        Per Vehicle 
          - Table - 5.3**Vehicle 
          Model Year**
        Total 
          Vehicles - Table - 5.4
        Miles 
          per Gallon - Table - 5.5
        Gallons 
          per Vehicle - Table - 5.6**Family 
          Income**
        Total 
          Miles Traveled - Table - 5.7
        Total 
          Gallons - Table 5.8
        Miles 
          per Household - Table - 5.9
        Gallons 
          per Household - Table - 5.10**Household 
          Composition**
        Total 
          Vehicles - Table - 5.11
        Miles 
          per Household - Table - 5.12**Miles 
          per Gallon**
        Per Vehicle 
          - Table - 5.13**Vehicle 
          Type**
        Total 
          Gallons - Table - 5.14
        Miles 
          per Vehicle - Table - 5.15
        Total 
          Vehicles - Table - 5.16**Number 
          of Households by Vehicle Fuel Expenditures**
        Number 
          of Households - Table - 5.17**Household 
          and Vehicle Energy Expenditures**
        Dollars 
          per Household - Table - 5.18**Row and Column Factors**
      These tables present estimates of characteristics, vehicle 
        fuel consumption, miles driven, and fuel efficiencies for all vehicles 
        used for personal transportation in the United States. Since the estimates 
        are based on a sample survey, they are subject to error. To help the reader 
        compute an approximate relative standard error (RSE) for each of the estimates 
        in the detailed tables, row and column factors are displayed on the top 
        line and in the far-right column of each table. To calculate the RSE for 
        a specific estimate, multiply the row factor by the column factor.
      **Using Row and Column Factors to Estimate the Standard 
        Error**
      RSEs were calculated for all statistics in this publication, 
        although they cannot be presented due to space limitations. However, the 
        RSEs are presented in a generalized form. The method of presenting generalized 
        RSEs of statistics uses sets of row and column factors inserted in the 
        top row and right-most column of figures in each table. This method of 
        presentation allows the readers to calculate an approximate RSE for each 
        statistic. To estimate the RSE of a statistic
      *RSEAij* =*Ri* X 
        *Cj* text box:Using Row and Column Factors to Estimate the Standard Error
      in the ith row and jth column of 
        a particular table, the approximation *RSEAi,j* for 
        the original *RSEi,j* is given by: Where: R*i* 
        is the RSE row factor given at the right-most margin of row i in the tables, 
        and C*j* is the RSE column factor given at the top of 
        column j. 
      
      The following 
        example illustrates this procedure:
      Referencing 
        the second row of Table 5.1 labeled "Northeast," and the third 
        column labeled "Vehicle-Miles Traveled (billion)," yields an 
        estimate of 299 billion miles driven. The RSE row factor is R2 
        = 5.7, and the RSEcolumn factor is C3 = 1.1. The approximate 
        RSE for the estimate is, therefore,
      *RSEA2,3 
        = 5.7 x 1.1 = 6.27 percent*
      The standard 
        error derived from row and column factors can be used to construct confidence 
        intervals and to perform hypothesis tests by standard statistical methods. 
        However, because the generalized variance procedure gives only approximate 
        RSEs, such confidence intervals and statistical tests must also be regarded 
        as only approximate. For the example above, the RSE determined directly 
        by the half-sample method is actually 3.9 percent, not 6.27 percent.
      **Determination 
        of the Standard Error of the Difference Between Two Statistics**
      The procedure 
        used to compute the standard error of the difference between two statistics 
        follows:
      
      This procedure 
        assumes the two statistics are not correlated. The following example illustrates 
        this procedure. Households with children drove an average of 24,800 miles 
        per household in 1994. Households without children drove an average of 
        18,900 miles, for a difference of 5,900 miles. The RSEs for households 
        with and without children are 2.7 and 4.6, respectively. The corresponding 
        standard errors are 670 miles and 869 miles, respectively. Therefore, 
        the standard error for the difference is:
      
      If 1.96 times 
        the standard error is greater than the difference between the statistics, 
        the difference is not statistically significant at the .05 level of significance 
        (the level used to test significance of inferences in this report). In 
        this example, 1.96 times the standard error equals 1,494 miles, while 
        the difference is 6,300 miles. Therefore, the conclusion is that, in 1994, 
        there was a significant difference in average mileage driven per household 
        between households with and without children.
      File Last 
        Modified: February 1, 2002
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