Do either of these census records look reasonable? I copied them just as they are indexed, not as they were written, to give you an idea of what sorts of problems one runs into. "Okal" in Arkansas is "Opal". Since she is 5 in 1930 she would have been born 1925, give or take a year or two.
The second family may not have gotten around to having Opal or Bernice yet.
I also changed the heading a bit. All of the posts here are about the McKnights. Using "McKnight" as a heading is like paying extra to have "Car For Sale" printed in big letters in your classified ad for selling a 1957 Chevrolet in the "Cars For Sale" column of the newspaper. You do better to pay extra to have "1957 Chevrolet" printed in big letters at the top of the ad.