How many dyslexics does it take to screw in a light bulb?
Dyslexia is a cognitive learning disability characterized by the sufferer's inability to fluently spell, speak and read. Being a intellectual disability, the chances that dyslexia could impair the practical functionality of a sufferer are very slim and hence it it is highly probable that it would only take one dyslexic to change a light bulb in the simplest of conditions.
However, to definitively answer this question, I would have to know a range of variables such as the height above the ground at which the light socket is mounted, the physical height of the dyslexic, the voltage and amp characteristics of the light-bulb itself, the physical well-being of the dyslexic etc. These variables are unknown, are not mentioned in the initial question (as is common for this type of question) and hence, I cannot answer this question to any degree of accuracy.