![]() The following missing value conventions are used throughout the data:įrequency Distribution:In the case of discrete (categorical) variables, frequency counts are normally shown in the first column to the left of the code categories. In a small number of variables, negative responses are possible users should check the minimum values allowed for each question to clarify whether negative numbers are permissible. Valid data are generally positive numbers. Note that rate of pay variables often have two implied decimal points. ![]() These variables have continuous data but are presented in the codebook using a convenient frequency distribution. Other dichotomous variables have frequently been reformulated to permit this convention to be followed.ĭiscrete (Categorical), as in the case of 'Month Enrolled in School.'Ĭontinuous (Quantitative), as in the case of 'Hourly Rate of Pay' in Figure 2. The following types of code entries occur in NLSY97 codeblocks:ĭichotomous (or variables answered yes/no), uniformly coded "Yes" = 1 and "No" = 0. For example, an additional code may be added during data processing if a significant number of respondents gave the same answer to the "other-specify" option in an answer list. If the two sources are different, the codebook is current and the questionnaire information should not be used in analysis. Coding information for a given variable in the NLSY97 codeblock is not necessarily consistent with the codes found within the questionnaire. Reference numbers may begin with R, S, T, U, Z, or E (E for Event History variables).Ĭoding Information:Each codeblock entry presents the set of legitimate codes that a variable may assume along with a text entry describing the codes. Generally, once assigned to the variables from an interview, reference numbers will never change unless there are special circumstances. Reference Number (RNUM): A reference number is a unique identifying number assigned to each variable in the data set. For more information on how question names are assigned, refer to Survey Instruments. ![]() In the second example, the question name CV_HRLY_PAY.01 indicates that the variable is created. In the first example, the question name YSCH-1400 shows that the variable is based on a question in the schooling section of the youth instrument. Questionnaire Item or Question Name: The question name provides the location of the question in the survey instrument or identifies it as a created variable. NLSY97 Questionnaire Item Codeblockįigure 2. Codeblocks for many variables also include special notes designed to assist in the accurate use of data. Each of the above terms is described more completely below. Codeblock entries depict the following important information: coding information, frequency distribution, questionnaire items, universe information, valid values range, and question text. The NLS Investigator software allows easy access to each variable's codebook information and permits the user to print a codebook extract for selected variables.Įvery variable is presented as a block of information called a "codeblock." Sample codeblocks are shown in Figures 1 and 2. The codebook is the principal element of the NLSY97 documentation system and contains information intended to be complete and self-explanatory for each variable in a data file. This section describes these three components of the NLSY97 documentation and discusses the important types of information found within each. Variables present in the NLSY97 main file are documented via (1) codebook (2) accompanying supplemental documentation and (3) error updates.
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