All these questions and more are answered in this book.
Children learn to read by sounding out new words bit by bit.
The subject is not merely of academic interest since reading is the most essential skill a child will ever learn and is the basis of all other education. The great difficulty at the time the book was written was that the existing research data was in hopeless conflict. Either side could point to dozens of studies proving their method to be best. Some studies received a lot of publicity. This had repercussions since textbook publishers used the research to produce reading series.