Final answer:
The mean of Joey's quiz grades is calculated by summing all the quiz scores and dividing by the number of quizzes. A hypothetical example yielded a mean of 75.07. For a true-false quiz with random guessing, probability principles are used to determine the chances of scoring at least 70% to pass.
Step-by-step explanation:
The question involves calculating the mean, or average, of Joey's quiz grades. To determine the mean quiz grade, we would sum all of Joey's quiz grades and then divide by the total number of quizzes Joey has taken. Without the actual quiz grades provided, I cannot perform the calculation, but I can explain the process with a hypothetical example. Suppose Joey's 14 quiz grades are as follows: 80, 73, 85, 90, 78, 75, 70, 88, 82, 77, 95, 69, 83, and 76. We would add these grades to get a sum of 1,051. Then we divide this sum by 14 (the total number of quizzes) to calculate the mean. Joey's average quiz grade, in this hypothetical case, would be 1,051 divided by 14, yielding a mean of 75.07.
If the question is about the likelihood of a student passing a quiz based on random guessing, we use probability. For a 10-question true-false quiz, there are two possibilities for each question (true or false). If a student guesses, there is a 50% chance of getting each question right. To pass with a 70%, the student needs to guess at least 7 out of 10 correctly. The calculation involves the binomial probability formula, which can be more complicated, but the basic principle is to determine the chances of achieving at least 7 correct guesses out of 10.