The Dale-Chall formula of 1948, which is based on sentence-length and percentage of words not found on the Dale Familiar Word List, yields a Raw Score that can be converted to the Grade Level (grade 4 to 16+) using a lookup table. The OKAPI! readability tool available online at http://www.interventioncentral.org/htmdocs/tools/okapi/okapi.php saves us a lot of time and trouble by performing these complex tasks.
I submitted for analysis the first 10 sentences of Jawaharlal Nehru’s ‘speech on the granting of Indian Independence’ and OKAPI! returned the following result:
Dale-Chall Readability Formula for This Passage = (0.0496 * 21.9 Avg. Number of Words Per Sentence) + (0.1579 * 18.72 Percent of Words in Sample Not Found on Dale Familiar Word List) + 3.6365 = 7.67 Raw Score = 9-10th Grade Level
If I were to use the formula without OKAPI!’s aid, I would even do without the lookup table by doubling the Raw Score and then subtracting 5 from the result (2 * 7.67 – 5 = 15.34 – 5 = 10.34). But calculating the Raw Score is not going to be easy. I, therefore, attempted and achieved a simplification. If AWS is the average words per sentence and PDW the percentage of non-Dale/difficult words, then
Direct Dale-Chall Grading (DDCG) = 0.1AWS + 0.3PDW + 3
Applying this simplified formula to the 10 sentences, I got DDCG = 10.806. No Raw Score and no lookup table — just Direct Dale-Chall Grading.
Here follows a comparison between the original formula and the DDCG for each of the 10 sentences.
1. Long years ago we made a tryst with destiny, and now the time comes when we shall redeem our pledge, not wholly or in full measure, but very substantially.
Raw Score = 8.34 (11-12th Grade Level)
DDCG = 12.104
2. At the stroke of the midnight hour, when the world sleeps, India will awake to life and freedom.
Raw Score = 6.28 (7-8th Grade Level)
DDCG = 8.133
3. A moment comes, which comes but rarely in history, when we step out from the old to the new, when an age ends, and when the soul of a nation, long suppressed, finds utterance.
Raw Score = 7.18 (9-10th Grade Level)
DDCG = 9.928
4. It is fitting that at this solemn moment we take the pledge of dedication to the service of India and her people and to the still larger cause of humanity.
Raw Score = 7.75 (9-10th Grade Level)
DDCG = 10.998
5. At the dawn of history India started on her unending quest, and trackless centuries are filled with her striving and the grandeur of her success and her failures.
Raw Score = 10.10 (16th Grade Level)
DDCG = 15.442 = 15+
6. Through good and ill fortune alike she has never lost sight of that quest or forgotten the ideals which gave her strength.
Raw Score = 6.16 (7-8th Grade Level)
DDCG = 7.927
7. We end today a period of ill fortune and India discovers herself again.
Raw Score = 6.71 (7-8th Grade Level)
DDCG = 8.914
8. The achievement we celebrate today is but a step, an opening of opportunity, to the greater triumphs and achievements that await us.
Raw Score = 9.03 (13-15th Grade Level)
DDCG = 13.381
9. Are we brave enough and wise enough to grasp this opportunity and accept the challenge of the future?
Raw Score = 8.03 (11-12th Grade Level)
DDCG = 11.466
10. Freedom and power bring responsibility.
Raw Score = 7.04 (9-10th Grade Level)
DDCG = 9.5
NOTE: The Direct Dale-Chall Grading grades texts from grade 4 to 15+. For the sake of accuracy, the DDCG result may be expanded to a grade-range (DDCG-1 to DDCG+1).