Skip to Main Content

DIBELS Initial Sound Fluency

LNF Timeline

Description of the ISF Measure

The DIBELS Initial Sound Fluency (ISF) Measure is a standardized, individually administered measure of phonological awareness that assesses a child's ability to recognize and produce the initial sound in an orally presented word (Kaminski & Good, 1996, 1998; Laimon, 1994). The ISF measure is a revision of the measure formerly called Onset Recognition Fluency (OnRF). The examiner presents four pictures to the child, names each picture, and then asks the child to identify (i.e., point to or say) the picture that begins with the sound produced orally by the examiner. For example, the examiner says, "This is sink, cat, gloves, and hat. Which picture begins with /s/?" The student then points to, or says the name of, the correct picture. The student is also asked to produce the beginning sound for an orally presented word that matches one of the given pictures. The examiner calculates the amount of time taken to identify/produce the correct sounds and converts the score into the number of initial sounds correct in a minute. The ISF measure takes about 3 minutes to administer and score, and has over 20 alternate forms to monitor progress.

DIBELS 6th Edition Technical Adequacy of the ISF Measure

Alternate-form reliability of the OnRF measure is .72 in January of kindergarten (Good, Kaminski, Shinn, Bratten, Shinn, Laimon, Smith, & Flindt, 2004). While that level of reliability is low with respect to standards for educational decision-making (e.g., Salvia & Ysseldyke, 2001), it is remarkable in a one-minute measure, especially one that can be repeated. By repeating the assessment four times, the resulting average has a reliability of .91 (Nunnally, 1978). The concurrent criterion-related validity of OnRF with DIBELS PSF is .48 in January of kindergarten and .36 with the Woodcock-Johnson Psycho-Educational Battery Readiness Cluster score (Good et al., 2004). The predictive validity of OnRF with respect to spring-of-first-grade reading on CBM ORF is .45, and .36 with the Woodcock-Johnson Psycho-Educational Battery Total Reading Cluster score (Good et al., 2004).

How does ISF link to the Big Ideas in Beginning Reading?

ISF is a measure that assesses phonemic awareness skills.

Phonemic Awareness (PA) is:

  1. the ability to hear and manipulate the sounds in spoken words and the understanding that spoken words and syllables are made up of sequences of speech sounds (Yopp, 1992).
  2. essential to learning to read in an alphabetic writing system, because letters represent sounds or phonemes. Without phonemic awareness, phonics makes little sense.
  3. fundamental to mapping speech to print. If a child cannot hear that "man" and "moon" begin with the same sound or cannot blend the sounds /rrrrrruuuuuunnnnn/ into the word "run", he or she may have great difficulty connecting sounds with their written symbols or blending sounds to make a word.
  4. a strong predictor of children who experience early reading success.

To learn more about phonemes, phonemic awareness, and how to design and implement effective phonemic awareness instruction, visit the Big Ideas in Beginning Reading website.

ISF Sample Clip