## Grading guidelines for the Math 135 final exam in spring 1998, with information about grades

### Background

The cover page states:
 Show your work. Full credit may not be given for an answer alone.
Therefore a "bald" answer with no supporting work may get little if any credit.

### General comments

Arithmetic errors will be penalized in the following way: -1 for the first error, and -1 for any additional errors. But students will need to follow the consequences - that is, they aren't allowed to just change their minds in the middle of a problem if their arithmetic errors have led to a more difficult situation to analyze than the correct one would have been!

Simplification is unnecessary unless specifically requested. So an answer which is (sqrt{3}+7)2 can be left that way instead of writing 52+14*sqrt{3} or the approximation 76.2487. The decimal number given is an approximation, and if an exact answer is requested, the approximation may be penalized. Rarely in this exam values of certain functions are supposed to be "simplified", such as in problems 2 and 11b) and 12. The statements of the questions should be a guide to that.

Other methods than are given in the "official" answers may certainly be valid strategies for these problems. The answers presented are not supposed to represent the only correct way. Valid solutions of any type will be graded in a manner similar to what is described below.

### Discussion of grading for each problem

1. (8 POINTS)
a) 3 POINTS for correct algebraic manipulation, and 1 POINT for the answer.
b) 3 POINTS for algebraic analysis (e.g., dividing top and bottom by x2, or writing that the dominant terms top and bottom are the x2 terms), and 1 POINT for the answer.

2. (12 POINTS)
4 POINTS for each asymptote: 2 POINTS for each answer which should be a correct equation (if the equation should be "x= -(1/2)ln 7", then "-(1/2)ln 7" alone loses 1 POINT), and 2 POINTS for showing SOME WORK. In this problem, computer evidence, since it is not specifically ruled out, is acceptable. But note again the cover page's declaration: "An answer alone may not get full credit." -1 POINT for not correctly simplifying the exp/ln computation.

3. (10 POINTS)
2 POINTS for the statement of the definition of f´(x) (leaving out "lim" in the definition loses 1 POINT). 8 POINTS for successfully manipulating the difference quotient and getting the derivative, but 0 POINTS for a correct answer which is not supported by algebra. As to the other 8 POINTS: 3 POINTS for validly replacing the definition by the specific function given, and 3 POINTS for doing valid algebra on it, and 2 POINTS for taking the limit correctly. POINTS to be taken off as described in the general comments for arithmetic errors, with more taken off for algebraic errors.

4. (12 POINTS)
a) 6 POINTS: 3 POINTS for writing correct conditions connecting A and B with numbers (take 2 POINTS off for the first mistake in an equation), and 3 POINTS for solving the system of equations written by the student correctly.
b) 6 POINTS: the graph should be continuous, otherwise -2 POINTS. 2 POINTS for the general shape (how it {in/de}creases: 1 POINT off for each error in this behavior). If not the graph of a function (that is, it is not "single-valued"), -2 POINTS.

5. (14 POINTS)
Parts a) and b) are each worth 4 POINTS. In each of these parts, -1 POINT for a minor error, and -2 POINTS for misuse of the chain/product/quotient rules. The last includes incorrect cancellations or combinations in and out of functions.
c) 6 POINTS (2 POINTS for successfully solving the differentiated equation for the derivative, -2 POINTS each for misuse of the product rule or chain rule). It is still possible to get 2 POINTS by solving for y´, though, even with a "broken" equation.

6. (15 POINTS)
a) 10 POINTS: 4 POINTS for computing the function value, and 4 POINTS for using the chain rule correctly to compute the derivative, and 2 POINTS for substituting values correctly to get the derivative.
b) 5 POINTS for some valid equation of the tangent line.

7. (14 POINTS)
3 POINTS for getting the correct value of r. 7 POINTS for either implicitly or explicitly getting a valid equation for r´ and then another 2 POINTS for finding the correct value of r´ "at that time". 2 POINTS for correctly responding to the {in/de}creasing question.

8. (26 POINTS)
a) 5 POINTS: These instructions are for version A where the derivative has two maximal open intervals indicated where it is negative and one where it is positive. Other versions will be graded in a similar fashion. 2 POINTS for saying where the function is increasing, and 1 POINT for saying why (sign of h´): we accept two adjoining intervals or one whole interval, and will also accept for reasoning h´ positive for the whole interval even though non-negative is sufficient. 1 POINT for saying where the function is decreasing, and 1 POINT for saying why (sign of h´).
b) 5 POINTS: 2 POINTS for the up-down-up nature of the graph and 3 POINTS for having 3 roots in (approximately) the correct places.
c) 6 POINTS: 2 POINTS for saying where the function is concave up and 1 POINT for saying why (sign of h´´). 2 POINTS for saying where the function is concave down and 1 POINT for saying why (sign of h´´).
d) 4 POINTS: 1 POINT for the relative extrema and its location, and 3 POINTS for the inflection points and their location.
e) 6 POINTS: 4 POINTS for each requested labeled point (there are three inflection points and one relative extremum) and 2 POINTS for the general shape of the curve. Please note that the points MUST be labeled ON the graph, and if they are not, the credit is NOT earned. Reason: credit was already earned for detecting the values of x in the section above. This section's answer tries to detect if students know what the picture of each behavior looks like.

9. (15 POINTS)
2 POINTS for the constraint (Pythagoras), 1 POINT for the constraint solved for one variable, 2 POINTS for the objective function (the area), 1 POINT for reducing the objective function to a function of one variable, 3 POINTS for differentiating the objective function correctly, 3 POINTS for finding out where the derivative is 0, and, finally, 3 POINTS for some explanation of why the answer found provides a minimum (note that ANY explanation using function limits or first derivative behavior or second derivative value is fine).

10. (8 POINTS)
a) 2 POINTS for computing the derivative.
b) 3 POINTS: remarking that the derivative is always positive gets 1 POINT. Students should give some indication of why for the other 2 POINTS. We do say that an answer alone may get no or reduced credit.
c) 3 POINTS: the answer must explicitly say that the function is increasing, and and indicate how this applies to get the result about the function values in the problem.

11. (12 POINTS)
a) 4 POINTS for getting the correct derivative.
b) 8 POINTS: 4 POINTS for using the Fundamental Theorem correctly: basically realizing the connection between the result of a) and this. 4 POINTS for evaluating correctly and completely. -1 POINT for not correctly evaluating the trig function each time.

12. (8 POINTS)
2 POINTS for the first correct antiderivative and 2 POINTS for evaluating the first constant of integration correctly. 2 POINTS for the second correct antiderivative and 2 POINTS for evaluating the second constant of integration correctly. -1 POINT for not evaluating the exponential function correctly.

13. (20 POINTS)
a) 2 POINTS for the sketch.
b) 8 POINTS: 4 POINTS for writing the correct definite integral and 4 POINTS for evaluating it. No "simplification" of the answer is required.
c) 10 POINTS: 4 POINTS for setting up the problem algebraically. For example, requiring that the integral from 0 to c be half the value found in b) or asking that the integral from 0 to c be the same as the integral from c to 2. 5 POINTS for working out the answer, and 1 POINT for the correct answer.

14. (16 POINTS)
a) 8 POINTS: 5 POINTS for the correct antiderivative and then 3 POINTS for the correct answer (which doesn't need to be "simplified").
b) 8 POINTS: -1 POINT if no "+ C" with an otherwise correct answer. If something blatantly horrid is written (e.g., integration as a multiplicative operation), 0 POINTS. -2 POINTS for each error of a multiplicative constant.

15. (10 POINTS)
a) 4 POINTS. The answer need not be computed entirely, but values of R should be inserted, otherwise -2 POINTS.
b) 4 POINTS for the answer: 2 POINTS if there is a difference of areas (as there should be), and 2 POINTS for writing the correct answer numerically. The answer doesn't need to be simplified.
c) 2 POINTS for the answer alone but just 1 POINT if the function value is NOT evaluated: e.g., R(the correct number).

## Discussion of the grades

A very large number of the final exams were graded in common using the guidelines above. The following information applies to those exams.

The grades ranged from 0 to 197, with a median grade of 82 and a mean grade of 84.3. The standard deviation was 39.3. A recommended translation from numerical final exam grade to letter final exam grade, along with the percentage of the students who got these grades are as follows:

 Numerical score Letter grade equivalent Percentage of all grades Low # High # 0 70 F 38.6 71 80 D 9.4 81 100 C 18.6 101 115 C+ 11.4 116 130 B 8.2 131 150 B+ 7.1 150 200 A 6.6

Overall the exam was comparable or even slightly easier than the fall semester's final exam, but performance on this exam was much poorer. The suggested letter grades reflect the desire to insure consistency of course standards.

There were several versions of the final exam. Grades on the versions seem to be statistically similar.

## What happens to the papers?

Rutgers regulations require instructional units to keep final exams for one year. Students who wish to inspect their exams should make appropriate arrangements with their instructors or with the Undergraduate Office of the Math Department.