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Column Editor Anne Marie Kotzer
Scientific Inquiry provides a forum to facilitate the ongoing process of questioning and evaluating practice, presents informed practice based on available data, and innovates new practices through research and experimental learning.
Quantitative research depends on identifying and measuring the right things. The process of measurement allows the researcher to determine if and in what quantity a characteristic is present. If the measurement is not correct, then the researcher may draw the wrong conclusion.
There are many forms of measurement. Some measures involve sorting subjects into categories; others quantify an objective characteristic. For example, using a thermometer measures the amount of heat in the body, whereas asking about religious affiliation seeks to categorize subjects based on their beliefs. Both types are frequently used in nursing practice.
Regardless of the type of measure, the researcher is interested in representing the characteristics of the subject accurately and consistently. The desirable characteristics of a measure are precision, reliability, and validity (Waltz, Strickland, & Lenz, 2004). All three are important in drawing accurate conclusions about the credibility of a research study.
Precision: A Focus on Reproducibility
When a measure is reproducible, that is, when it generates a consistently accurate value every time it is used, it is considered precise. The reader can have confidence that differences between individuals are not explained by differences in the measurement instrument. Both reproducibility and accuracy must be present for a measure to be precise. For example, a tape measure is often used to measure the length of a neonate. A tape measure that has been used repeatedly may become stretched. While it may be a consistent measure of neonatal length, it is not an accurate one; it will consistently underestimate the neonate's length. Likewise, using a metal yardstick yields an accurate result, but it is unlikely that the nurse will have a quiet baby lying on the instrument each time it is used. While the metal yardstick might be accurate, results are not reproducible. Both characteristics - reproducibility and accuracy - are necessary to describe a measure as precise.
The most common way to assure precision is through calibration of instrumentation. Calibration is accomplished by measuring a known quantity of a variable and determining if the instrument generates identical...