Vocabulary is very important for everyday reading because it includes all the words of a language. According to Bursuck and Damer (2010) as students “learn to decode more difficult texts, they are more likely to encounter words that are not part of their oral language” (p. 231). Being familiar with words and their meanings promotes student fluency and understanding. According to the National Institute of Literacy (2007) vocabulary is “words used in speech and print to communicate” (p. 14). Vocabulary can be divided into two categories “oral or spoken words and written words” (National Institute of Literacy, 2007, p. 14). The National Institute of Literacy (2007), agrees with Bursuck and Damer (2010), stating that “vocabulary knowledge is important for reading because oral and written words promote comprehension and communication” (p. 14). Because vocabulary is extremely important, Pullen, Tuckwiller, Konold, Maynard, & Coyne, 2010 used a “three-tier model for students at risk for reading disabilities” (p. 110). Pullen et al. (2010) states that vocabulary development occurs through incidental learning and the home environment prior to formal education” (p. 111). The intervention created by Pullen et al. (2010) was intended to increase the vocabulary of at-risk students. Intervention participants (2010) “were 224 first-grade elementary school students in a diverse population with a moderate percentage of students in socioeconomic status” (p. 114). The intervention itself (2010) created by ___________________ was a three-tiered system: Tier 1 consisted of classroom instruction and “students who do not respond to Tier 1 will receive Tier 2 instruction, and Tier 3 is the tier more intense and if the student does not respond to this level they are referred for a special education evaluation” (p. 114). To identify students who may be at risk for a disability, the intervention (2010) used the PPVT-4 as a standardized test. Pullen et al. (2010) used the test to assess baseline levels “of receptive vocabulary and identify participants as at risk or not for reading failure” (p. 115). The intervention authors (2010) selected the PPVT-4 because it “has demonstrated reliability, indicating that it is a valid measure for measuring receptive vocabulary” (p. 115). For a posttest, the authors (2010) used a researcher-developed measure to assess students' acquisition of the target words used in the intervention (p. 115). Pullen et al. (2010) had a three-tier system in which Level 1 and Level 2 were designed “around two storybooks appropriate for first-grade students” (p..