Final answer:
The perplexity of a string of characters randomly sampled from the alphabet [a-z] is 26, assuming each character is equally likely to be chosen.
Step-by-step explanation:
The perplexity of a string of characters randomly sampled from the range [a-z] is 26. This is because when characters are sampled randomly and independently from a set of 26 characters, there is an equal probability of each character being selected. Perplexity, in the context of probability and information theory, is a way of measuring how well a probability distribution or probability model predicts a sample. It is defined as the exponentiated average negative logarithm of the probability distribution. In the case of a uniform distribution over 26 characters, perplexity is the 26th root of 26 raised to the 26th power, which is just 26.