Quick example: when I fist started liking cars (technical aspect) about 3 years ago (Im 19 now), I thought that 14:1 meant the compression ratio for every engine, or most of the engines made, and I "knew" this because I researched it. I thought this for a long while (most likely 4 or 5 months). I then found out that 14:1 is the atmospheric pressure at sea level. Actually, it is 14.7 lbs/in2, or one atmosphere. Its not even written the same (14:1 - a ratio, and 14.7 - a decimal). See what I mean? I searched and searched for some time to find out what 14:1 meant, and the whole time I was wrong.