SMOG

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Educational Psychology: Assessment · Issues · Theory & research · Techniques · Techniques X subject · Special Ed. · Pastoral

SMOG (Simple Measure of Gobbledygook) is a readability formula that estimates the years of education needed to completely understand a piece of writing. SMOG is widely used, particularly for checking health messages.[1] [2] The SMOG formula 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.[3]

SMOG was published by G. Harry McLaughlin in 1969 as a more accurate and more easily calculated substitute for the Gunning-Fog Index. To make calculating a text's readability as simple as possible an approximate formula was also given — 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.

Applying SMOG to other languages[4] lacks statistical validity.

FormulasEdit

To calculate SMOG

1. Count a number of sentences (at least: 10 from the start of a text, 10 from the middle, and 10 from the end).
2. In those sentences, count the polysyllables (words of 3 or more syllables).
3. Calculate using
$\mbox{grade} = 1.0430 \sqrt{ 30\times\frac{\mbox{number of polysyllables}}{\mbox{number of sentences}} } + 3.1291$

A version is also given which is more easily used for mental math and is sometimes known as the SMOG Index:

1. Count the number of polysyllabic words, excluding proper nouns, in a sample of thirty sentences.
2. Take the square root of the nearest perfect square