Acquiring an extensive vocabulary can have an enormous effect on one’s comprehension, fluency, and the ability to speak effectively to others. One way to acquire this widespread vocabulary is through reading a wide array of texts. Words are encountered and meshed into one’s internal word bank through independent reading. Likewise, lifelong love of reading promotes one’s vocabulary acquisition because repeated exposure to vocabulary in various contexts helps students learn words (National Reading Panel, 2000).

The purpose of this study was to measure the effectiveness of independent reading on fourth-grade students’ vocabulary acquisition, fluency rate, and overall comprehension. It was conducted with two groups of fourth-grade students. The control group had regular study hall classes each day. The treatment group had twenty minutes of independent reading time built into their school day during the study hall period.

Data were collected through the use of the Accelerated Reader program, which not only tracks the books read and measures comprehension but also cumulatively counts the numbers of words in the readings. The Peabody Picture Vocabulary Test, which measures vocabulary acquisition from birth to 99 years of age, was given as a pretest (August) and posttest (December) to both groups. Pre- and posttest scores from Dynamic Indicators of Basic Early Literacy Skills (DIBELS) Oral Reading Fluency (ORF) were used to measure students’ reading accuracy and speed as indicated by the number of words read correctly in one minute. The Degrees of Reading Power (DRP), which is a criterion-referenced test, was used to measure students’ gains in reading comprehension from pre- to posttest, and the DRP provided holistic measures of how well students understood the meanings of leveled passages.

The results of this study indicated that independent reading time can significantly improve fluency as well as the total number of words read for fourth graders in books for which they took and passed Accelerated Reader tests. No significant differences were found between the treatment and control groups for vocabulary acquisition or comprehension as individual components of reading achievement.