User Guide for the TIMSS International Database.pdf - TIMSS and ...

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C H A P T E R 3 S A M P L I N G MATWGT This weight is computed by dividing the sampling weight for the student by the number of mathematics teachers that the student has. This weight should be used whenever the user wants to obtain estimates regarding students and their mathematics teachers. SCIWGT This weight is computed by dividing the sampling weight for the student by the number of science teachers that the student has. This weight should be used whenever the user wants to obtain estimates regarding students and their science teachers. TCHWGT This weight is computed by dividing the sampling weight for the student by the number of mathematics and science teachers that the student has. This weight should be used whenever the user wants to obtain estimates regarding students and their mathematics and science teachers combined. The Student-Teacher Linkage file also includes variables that indicate the number of mathematics teachers, the number of science teachers, and the number of mathematics and science teachers the student has. 3.10 Weight Variables Included in the School Data Files The TIMSS samples are samples of students within countries. Although they are made up of a sample of schools within the countries, the samples of schools are selected so that the sampling of students, rather than the sampling of schools, is optimized. In other words, the samples are selected to make statements about the students in the country rather than about the schools in the country. To this effect, several weight variables are included in the school files. These variables are listed below. WGTFAC1 School Weighting Factor This variable corresponds to the inverse of the probability of selection for the school where the student is enrolled. WGTADJ1 School Weighting Adjustment This is an adjustment that is applied to WGTFAC1 to account for non-participating schools in the sample. If we were to multiply WGTFAC1 by WGTADJ1 we would obtain the sampling weight for the school adjusted for non-participation. SCHWGT School-level Weight The school sampling weight is the inverse of the probability of selection for the school, multiplied by its corresponding adjustment factor. It is computed as the product of WGTADJ1 and WGTFAC1. Although this weight variable can be used to estimate the number of schools with certain characteristics, it is important to keep in mind that the sample selected for TIMSS is a good sample of students, but not necessarily an optimal sample of schools. Schools are 3 – 1 8 T I M S S D A T A B A S E U S E R G U I D E
S A M P L I N G C H A P T E R 3 selected with probability proportional to their size, so it is expected that there is a greater number of large schools in the sample. STOTWGTL Sum of the Student Weights for the Lower Grade STOSWGTU Sum of the Student Weights for the Upper Grade STOTWGTE Sum of the Student Weights for the Extra Grade 5 These variables are the sum of the weights of the students in the corresponding grade level within the school. If there are no students at this grade level, then the variable is set to zero. These variables can be used to conduct analyses on questions like “How many students attend schools that have a certain characteristic?” Although weight variables have been included in the school files, there is no information in these files regarding the sampling zone in which the school is included (see Chapter 8 for discussion of sampling zones in the estimation of sampling variance). If the user is interested in computing proper standard errors of the population estimates, then the information in the school file should be merged with the student file and the analysis conducted using a student-level file. 5 Students in the extra grade are those students above the upper grade in the TIMSS sample. Sweden and Switzerland tested students at this grade level and those data are included in the database. T I M S S D A T A B A S E U S E R G U I D E 3 – 1 9
Page 1 and 2: International Association for the E
Page 3 and 4: Contents Chapter 1: Overview of TIM
Page 5 and 6: C O N T E N T S 7.3 Codebook Files
Page 7 and 8: C O N T E N T S Table 7.7 Classific
Page 9 and 10: Chapter 1 Overview of TIMSS and the
Page 11 and 12: I N T R O D U C T I O N C H A P T E
Page 17 and 18: Chapter 2 TIMSS Instruments and Boo
Page 19 and 20: I N S T R U M E N T S C H A P T E R
Page 29 and 30: Chapter 3 Sampling and Sampling Wei
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Page 35 and 36: S A M P L I N G C H A P T E R 3 3.5
Page 37 and 38: S A M P L I N G C H A P T E R 3 Fig
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C H A P T E R 9 P E R F O R M I N G
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R E F E R E N C E S Gonzalez, E.J.
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R E F E R E N C E S Wilson, M.R. (1
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A C K N O W L E D G M E N T S Inter
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A C K N O W L E D G M E N T S Latvi
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A C K N O W L E D M E N T S TIMSS A
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A C K N O W L E D G M E N T S Quali
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