Based on the informal reading inventories I have given over the years to elementary students is the actual inventory. For example, one passages the students had to read mentioned a fife. Well, not many of the students knew what it was, while a few figured out that it was some type of musical instrument. Other inventories use made up words. Well, to a good reader they know words are suppose to make sense so they read the word as a real word. For example, if the nonsense word was "git", some children would read it as "get".
Another factor is the administrator. I saw one teacher mark a student's answer incorrect because the answer wasn't exactly like the one in the answer book. The question was where did the story take place. The girl answered on a farm. The teacher said no it happened in the country. Later on the teacher asked to describe the main character. The little girl said it was a farmer who plow the crops. That answer was correct. The story did take place in the county, but most of it took place on the farmer's farm.
I think when giving an informal reading inventory the administrator needs to be observant. Listen as the child reads aloud. Is he reading fluently? Is he reading all of the words, but doesn't understand the passage? Does the child go back a fix his mistake if he read the word incorrectly and knows now that it doesn't make sense? Then make additional notes so when meeting with parents, you can explain the score.
I'd like to know what others think about this question.