A readability formula designed to estimate the years of education required for a reader to fully understand a text. Developed by G. Harry McLaughlin in 1969, its calculation is primarily driven by the density of polysyllabic words (words containing three or more syllables). Because it aims for 100% comprehension rather than a 50-75% passing understanding, SMOG often provides a more conservative, higher-grade-level estimate than other formulas. It is frequently used in the healthcare and legal sectors, where total clarity is essential.
History and Development
SMOG was developed by G. Harry McLaughlin as a more accurate and easily calculated substitute for the Gunning fog index. Published in 1969, the formula was designed to estimate the years of education needed to understand a piece of writing. It is widely used, particularly for checking health messages.
- Correlation: The SMOG grade yields a 0.985 correlation with a standard error of 1.5159 grades with the grades of readers who had 100% comprehension of test materials.
- Approximate Formula: To simplify calculation, an approximate formula was also provided: count the words of three or more syllables in three 10-sentence samples, estimate the count’s square root (from the nearest perfect square), and add 3.
Applications
SMOG is particularly useful in fields where clarity is crucial, such as healthcare and legal sectors. Its conservative estimates ensure that texts are accessible to readers with the appropriate level of education.
- Healthcare: SMOG is often used to evaluate the readability of health messages, ensuring that important information is understandable to the intended audience.
- Legal: In the legal sector, SMOG helps ensure that documents are clear and comprehensible to individuals with varying levels of education.
Comparison with Other Readability Formulas
SMOG is known for providing higher-grade-level estimates compared to other readability formulas. This is because it aims for 100% comprehension, making it a more stringent measure.
- Gunning Fog Index: SMOG was developed as a more accurate and easily calculated alternative to the Gunning Fog Index.
- Flesch-Kincaid: Unlike the Flesch-Kincaid formula, which considers sentence length and syllable count, SMOG focuses solely on the density of polysyllabic words.
