def experience_boost_determination(ability_scores, prime_ability):
    """
    This function determines any applicable experience boost.
    Assumes abilities is a list of tuples (ability as str, stat as int)
    Assumes prime_ability is a string.
    Returns a percentage as a str.
    """
    abilities = ['Strength', 'Intelligence', 'Wisdom', 'Dexterity', 'Constitution', 'Charisma']
    stats = ability_scores
    prime = abilities.index(prime_ability) 
    if stats[prime][1] == 13 or stats[prime][1] == 14:
        experience_boost = '5%'
    elif stats[prime][1] >= 15:
        experience_boost = '10%'
    else:
        experience_boost = '0%'
    return experience_boost