A teaching assistant gives a quiz. There are 10 questions on the quiz and no par
ID: 3226902 • Letter: A
Question
A teaching assistant gives a quiz. There are 10 questions on the quiz and no partial credit is given. After grading the papers the TA writes down for each student the number of questions the student got right and the number wrong. What is the correlation of the number of questions right and wrong? You need to explain how you got your answer to receive credit.
Hint: Make up some data for number of questions right, calculate number of questions wrong, and plot them against each other.
oooo o o o o 982200 OC OD A. A OC OB OC, OD 15 000 q'q'q' 16 OC OA OD AT 08 OA OC, DO 18 08 OA OC, OA 00 0.0 0 0.0Explanation / Answer
Sample data:
The average number of right answers is 6.4 with an SD of 2.0; the average number of wrong answers is 3.6 with the same SD of 2.0
The relationship between the number wrong and the number correct can be described with a line.
Number Correct = 10 - Number Wrong
This is the equation of a line with slope equal to -1 and intercept equal to 10. The data for each student will fall exactly on this line..Because for every answer you get right out of 10 you get one less wrong out of 10. For example, if you got 6 correct and 4 wrong, then getting 1 more right at 7 then you got 1 less wrong at 3.
The slope equals (r)(std dev of y) / (std dev x) = 1, but we know that std dev is 2 for both x and y. That means r must equal -1, Hence the correlation must be -1
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.