An average sentence should have an ELF score below 12 for easy listenability. Fang found a correlation of .96 between his formula and Flesch's Reading Ease formula on 36 television scripts and 36 newspaper samples.

Subsequent research into listenability indicates that after the 8^th grade, listening skills do not keep up with the improvement in reading skills. After the 12^th-grade level, the same text may be harder to understand when heard than when read (Chall 1983b; Dale and Chall 1995; Sticht, Beck, et al. 1974).

The SMOG formula G. Harry McLaughlin (1969) published his SMOG formula in the belief that the word length and sentence length should be multiplied rather than added. By counting the number of words of more than two syllables (polysyllable count) in 30 sentences, he provides this simple formula:

SMOG grading = 3 + square root of polysyllable count.

McLaughlin validated his formula against the McCall-Crabbs passages. He used a 100 percent correct-score criterion. As a result, his formula generally predicts scores at least two grades higher than the Dale-Chall formula.

The FORCAST formula The Human Resources Research Organization studied the reading requirements of military occupational specialties in the U.S. Army (Caylor et al. 1973). In order to resolve professional questions about using a formula for technical material read by adults, the authors first undertook the creating of a readability formula that would be:

1. Based on essential Army-job reading material.
2. Adjusted for the young adult-male Army-recruit population.
3. Simple and easy for standard clerical personnel to apply without special training or equipment.

The researchers first selected seven high-density jobs and 12 passages that recruits are required to understand to qualify for them. They graded the passages with the modified Flesch formula, finding them to range from the 6^th to the 13^th grade in difficulty. They also selected 15 text variables to study for a new formula. They next tested the reading ability of 395 Army recruits, and then divided them into two groups, one with a mean-grade reading level of 9.40 and another 9.42.

They next tested the recruits with cloze tests made of the 12 passages. The 12 passages were then re-graded using the criterion of at least 50% of those subjects of a certain grade level being obtaining a cloze score of at least 35%. Results indicated that average subjects scored 35.1% on the text graded 9.1 and 33.5% on the text graded 9.6.

They next intercorrelated the results of the reading tests with the results of the graded cloze tests. Results showed usable correlations of .83 and .75 for the two groups of readers. Among the 15 variables they examined, the number of onesyllable words in the passage correlated highest (.86) and was selected for use in their new formula. Because they found that adding a sentence factor did not improve the reliability of the formula, they left it out. The resulting FORCAST formula is:

Grade level = 20 - ( N ÷ 10 )

Where N = number of single-syllable words in a 150-word sample.