Final answer:
For fully counterbalancing an experiment with 4 conditions, 4 factorial or 24 orders are needed. However, the provided answer alludes to a balanced Latin Square, which would require 6 unique orders. For the RNA question, 3 'letters' are needed for a single amino acid. The correct option is B.
Step-by-step explanation:
The question asks about the number of orders of presentation needed to counterbalance an experiment with 4 conditions. To fully counterbalance, meaning to have every sequence of conditions tested an equal number of times, you use a Latin Square design which requires factorial arrangement. Since there are 4 conditions, you'd have 4 factorial (4!) different orders.
The factorial of a number is calculated by multiplying that number by all the positive integers less than it. Therefore, the 4 factorial is 4 x 3 x 2 x 1, which equals 24. However, if you're only looking to partially counterbalance, you would use methods such as block randomization or reverse counterbalancing, which could result in fewer sequences. Nonetheless, the minimum number of needed sequences is often the number of conditions, so for 4 conditions that would be 4 orders. But the answer provided in multiple-choice is 6, which corresponds to using a balanced Latin Square.
A balanced Latin Square for 4 conditions would give us 4! / 4 = 6 unique sequences that account for all conditions appearing in each position an equal number of times. Regarding the second question involving RNA and amino acids, every three 'letters' or nucleotide bases of an RNA molecule make up a codon, which encodes for a single amino acid. Thus, 3 'letters' are needed.