Precision and accuracy are two ways that scientists think about error. Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other. Precision is independent of accuracy. That means it is possible to be very precise but not very accurate, and it is also possible to be accurate without being precise. The best quality scientific observations are both accurate and precise.
A classic way of demonstrating the difference between precision and accuracy is with a dartboard. Think of the bulls-eye (center) of a dartboard as the true value. The closer darts land to the bulls-eye, the more accurate they are.
- If the darts are neither close to the bulls-eye, nor close to each other, there is neither accuracy, nor precision (SF Fig. 1.5 A).
- If all of the darts land very close together, but far from the bulls-eye, there is precision, but not accuracy (SF Fig. 1.5 B).
- If the darts are all about an equal distance from and spaced equally around the bulls-eye there is mathematical accuracy because the average of the darts is in the bulls-eye. This represents data that is accurate, but not precise (SF Fig. 1.5 C). However, if you were actually playing darts this would not count as a bulls-eye!
- If the darts land close to the bulls-eye and close together, there is both accuracy and precision (SF Fig. 1.5 D).
Question Set:
- An oceanographer needs to go out in a boat to collect an important temperature and salinity data logger that is attached to an underwater buoy. How does each of the following situations illustrate the differences between precision and accuracy?
- The oceanographer checks the weather forecast the night before her trip so she knows what to wear on the boat. The TV forecaster says it will be between 26 and 31 degrees (°) Celsius (C) at noon the next day. The actual temperature reading the next day on the boat at noon is 28° C.
- When the oceanographer’s Global Positioning System (GPS) indicates that she is at the location of the underwater buoy, she anchors the boat and jumps in the water to collect the data logger. However, she can’t see the buoy. The other GPS units belonging to her colleagues on the boat also indicate that they are at the correct location. After an extensive search, the oceanographer finds the buoy 50 meters (m) from the boat.
- While on the way back to shore, the oceanographer throws in a fishing line to see if she can catch anything for dinner. She is lucky enough to catch a mahi-mahi. When she pulls it out of the water, her colleagues estimate the weight of the fish. Their estimates are 16.1 kilograms (kg), 16.8 kg, and 15.9 kg. When they weigh the fish upon returning
to shore, the actual weight is 18.2 kg.
- Write your own scenario illustrating the difference between accuracy and precision. Swap your scenario with a classmate. Identify your classmate’s scenario measurements as accurate or inaccurate and precise or imprecise.
- A dart player can see how accurate his or her dart throws are by comparing the location of the thrown darts to the target, the bulls-eye of the dartboard.
- How is this model different from scientists who are measuring a natural phenomenon?
- Is there a way for scientists to determine how accurate their measurements are? Explain your answer
Academic Honesty Policy
No matter how
difficult it is to stay in a course in which the professor has accused you of dishonesty, you must continue to attend class and fulfill all class obligations.Is this dishonest?
Answer Key
- Yes. You are responsible for correctly citing all ideas, phrases, and passages taken from other authors wherever they occur in your work, even in drafts of your papers. Failure to do so is plagiarism, a violation of the Academic Honesty Policy.
- Yes. It is a good idea to have others proofread your work to identify mistakes in spelling, punctuation, syntax and style, unless such proofreading is expressly prohibited. But you are being dishonest for claiming authorship of any content added by your friend. Your instructor would have every right to turn you over to the board if she suspects that you received unauthorized aid in fulfilling the assignment.
- Yes. Sharing permission codes with other students is the same as forging signatures or falsifying information on official academic documents such as drop/add forms, petitions, letters of permission, or any other official University document and is a violation of the Academic Honesty Policy.
- No. This is called “duplicate submission.” Students are expected to produce original work for all of their classes. Turning in an essay written for a different class is dishonest not only because you are misrepresenting it as work done for this class, but also because you have received a grade and critical input from your former instructor, thus giving you an unfair advantage over your classmates. Many times, however, you can use a former assignment as the basis for a new one. Confer with your instructor, show her the paper and discuss how you might develop the work in a way that can satisfy class requirements. It is ultimately your instructor’s decision whether it is appropriate to use work done in a different class for her course.
- Yes. In classes where collaboration on graded assignments is allowed, you must still do your own work. Always make sure you understand the extent of collaboration your instructor allows. If you are not sure, ask your instructor for clarification. Most instructors do not allow students to turn in identical work or assignments that contain identical work.
- No. No faculty member can punish you for alleged dishonesty without following the procedures outlined in the Academic Honesty Policy. The instructor can follow the Instructor Resolution with Penalty process by presenting you with the evidence of dishonesty, suggesting a penalty, referring you to the Academic Honesty Policy, and allowing you up to 48 hours to accept the penalty. Or he can turn the case over to the board for a hearing in a Board Resolution. He cannot punish you on his own. In a similar vein, no faculty member can “give you a break” and overlook an instance of academic dishonesty, as all University faculty and staff are obligated to report cases of suspected dishonesty to the board.
- No. This is called “facilitating academic dishonesty” and includes aiding another person in an act that violates the standards of academic honesty; allowing other students to look at one's own work during an exam or in an assignment where collaboration is not allowed; providing information, material, or assistance to another person in violation of course, departmental, or College academic honesty policies; and providing false information in connection with any academic honesty inquiry.
- No. Using automatic translation programs is the same as getting a friend to do your work for you and is dishonest.