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Coverage, sampling, reliability, and nonresponse issues, by education system: PIRLS 2021

Coverage			Sampling		Reliability		Nonresponse
Coverage			Sampling		Reliability		Figure 2—School operations affected by COVID-19		Figure 4—Students Like Reading Scale	Figure 5—Students Confident in Reading Scale	Figure 6—Instruction Affected by Reading Resource Shortages Scale
National Target Population does not include all of the International Target Population.	National Defined Population covers 90 to 95 percent of National Target Population.	National Defined Population covers less than 90 percent of National Target Population (but at least 77 percent).	Met guidelines for sample participation rates only after replacement schools were included.	Did not satisfy guidelines for sample participation rates.	Reservations about reliability because the percentage of students with achievement too low for estimation exceeds 15 percent but does not exceed 25 percent.	Reservations about reliability because the percentage of students with achievement too low for estimation exceeds 25 percent.	Data are available for at least 70 percent but less than 85 percent of the students.	Data are available for at least 50 percent but less than 70 percent of the students.	Data are available for at least 70 percent but less than 85 percent of the students.	Data are available for at least 70 percent but less than 85 percent of the students.	Data are available for at least 70 percent but less than 85 percent of the students.	Data are available for at least 50 percent but less than 70 percent of the students.

NOTE: Only education systems with coverage, sampling, or reliability issues are included in the table. The guidelines for sample participation rates specify that the minimum acceptable participation rates were 85 percent of schools, 95 percent of classes, and 85 percent of students, or a combined rate (the product of school, class, and student participation) of 75 percent. Education systems administered PIRLS 2021 in one of three waves: Wave 1 occurred as originally planned with 4th-grade students at the end of the 2020–21 school year; Wave 2 occurred six months after the original plan with 5th-grade students at the beginning of the 2021–22 school year; and Wave 3 occurred one year after the original plan with 4th-grade students at the end of the 2021–22 school year. The Wave 2 education systems are shown with a “(5)” notation. Brazil, England-GBR, Israel, and South Africa administered PIRLS in Wave 3. Education systems that are not countries are designated by the appended three-letter international abbreviation for their country. Benchmarking participants are indicated with italics.

SOURCE: International Association for the Evaluation of Educational Achievement (IEA), Progress in International Reading Literacy Study (PIRLS), 2021.