<labrqmts04.doc>jlt04
LAB REPORT REQUIREMENTS FOR PHYSICS
Labs are your floatation devices in case of an emergency landing into the icy waters of physics. Physics is a lab course. The labs occur frequently and they determine a significant portion of your grade. The following instructions indicate how lab reports are to be written and describe the sections that must comprise all lab reports. This reference is to be carefully read and followed precisely so as not to puncture your floatation device.
GENERAL REQUIREMENTS:
Lab reports are to be individually written and turned in on loose-leaf. After your lab is graded and returned, it is to be fastened into a lab folder in reverse chronological order (newest lab on top). The folder will be periodically graded for neatness and completeness.
The individual lab reports are to be neat and well organized. Spelling and basic grammar are considered in the grading process. You are encouraged to word-process text portions and spreadsheet tabular data/results if you have such access.
Labs will be due at the beginning of the class period on the designated due date. All pages must be stapled together in the correct order. Labs not turned in at the beginning of the period are considered late. One-third of a letter grade will be deducted if the lab is turned in later on the same day it is due. One whole letter grade will be deducted for each school day the lab is late. Incomplete labs will be returned without grade and will be considered late. Missing or incomplete labs count as zero until they are completed and submitted. If you are absent on the day the class performs a lab, you must see your instructor to schedule lab time after school. You should plan on having your lab made up and turned in promptly following any absence. If you are absent (full day) on the due date, your lab is to be turned in promptly on your return to school.
Portions of the lab must be prepared prior to entering the lab. On the day of a lab, you are expected to come prepared with the title, purpose, procedure, and data tables ready to accept data. These will be date stamped in the lab after data collection has been completed. Work neatly – these stamped sheets must be included in the final report.
It is important that you do your own work. It is expected that you and your partner will have identical lab data, since you are working jointly to collect it. However, splitting the calculations with your partner then sharing your answers is considered cheating. Copying another student's calculations, spreadsheets, graphical results, conclusions, or answers to questions is considered cheating. Changing a word or two in an attempt to cover up copying another student's ideas is cheating. There are consequences. Why should I even have to say this??
LAB REPORT FORMAT:
You should assume the audience for the lab report is a technically competent client who has hired you as a laboratory consultant. The client knows and understands the overall purpose of the work, but does not necessarily know the details of what you have done. All of the following sections must be included in your report in the designated sequence. Sections 1-4 must be prepared prior to entering the lab.
1. TITLE/AUTHOR: a short title suggestive of the lab being performed. No separate cover sheet is necessary. Spend time on the lab contents - not on fancy artwork. Of course, your name should be included prominently nearby, along with the name of the person who was your "partner" in the collection of data. This partner must have been assigned/approved by your instructor and present in the lab with you. If your partner is absent the day of the lab, he/she must perform the lab after school to obtain separate data. Make it clear whose lab I'm reading.
2. PURPOSE: a description of what is to be determined or verified by doing this lab. There should be a way of telling whether or not the purpose was achieved, so be concrete. A purpose such as "experimentally verify the acceleration of gravity" is useful: "become acquainted with falling objects" is useless!
.3. PROCEDURE: a sequence of steps that describe how the lab is performed. Someone else should be able to perform the lab reading only your procedure. Include a materials list and a diagram if appropriate. Also include brief statements of how the data will be analyzed to achieve the purpose. The procedure is in your own words. You may NOT scan/OCR the lab handout sheet or copy from anyone else.
4. DATA TABLES: organized tables prepared with a ruler with labels and units for the measurements to be made in the lab. Results of subsequent calculations may be included in the data tables alongside the data. A unified data/results table makes the lab much easier to follow. Think ahead! Organize! You may even want to prepare blank tables using a spreadsheet. The goal is to come into lab knowing what data needs to be collected and where to put it in your table. Note that the data table you fill out in lab must get stamped and is a required element of the final report, even if you type it into a spreadsheet later. This original handwritten data must sequentially precede any recopied/spreadsheet versions.
5a. SAMPLE CALCULATIONS: done AFTER data collection is complete. Neatly organize and label what is being calculated, what formula is being used, and show a sample of the calculation using your numbers with the correct units. E.g., if you need to repetitively compute the volume of a block, you only need to show how this is done once. The results of other similar calculations may then be tabulated into your tables. If you use a spreadsheet to produce your data/results table, you'll still need to show me a sample calculation. Handwritten sample calcs are preferred – it takes too much time to properly format mathematical expressions using a computer. Results of all calculations are to be shown to the correct number of significant figures.
5b. GRAPHS: All graphs must be done on graph paper and include: a title; axes labels; axes units; uniform axis scaling appropriate to the range of data to be plotted such that the graph area occupies at least half a page – bigger is better; data points shown with clearly marked points and protectors; best-fit line or curve – make it smooth, not "connect the dots" (Use a ruler or French curve.); point coordinates used for slope identified (not data points, but other well separated points on the line); slope calculation performed on the graph in an open area – include appropriate units. Consult the handout titled "Graphing Techniques" for further explanation. Computer generated graphs may be used, but any slope calculation must be done by YOU directly on the graph. Computer generated graphs must display sufficient grid lines to allow for accurate slope calculation.
6. ERROR ANALYSIS: Almost every lab involves the computation of a "percent error" to demonstrate how well an experimental result matches up with a predicted result. This error is calculated by computing the absolute value of a fraction whose numerator is the difference between accepted and experimental values and whose denominator is the accepted value itself. We convert this fraction into a percent by multiplying by 100%. Lower values are generally "better" in the sense that this shows closer agreement between predicted and actual results, but experimental error is never totally avoidable.
Random errors are statistical in nature, fluctuating in magnitude and sign. Because of the precision limits of measurement equipment (e.g., meterstick + .05cm) or possible parallax in reading an instrument, a repeated measurement may be slightly high or low each time. This uncertainty is reduced by minimizing certain kinds of parallax, using higher precision instruments and averaging repeated measurements.
Systematic errors are likely to be constant and in the "same direction" due to apparatus problems or flaws in the measurement technique or situation. An example of this would be an offset error in using a micrometer that does not close to zero. Another example is the effect of friction on moving objects. This type of uncertainty can be reduced by minimizing the effects of offsets and certain kinds of parallax or recognizing how the equipment could be more carefully used.
Mistakes are not considered as scientific error. Mistakes CAN be eliminated altogether. If a mistake is discovered in the performance of the lab, the affected procedure can be repeated. There is never an excuse for mistakes in calculations. You have sufficient time to check over your calculations and purge out mistakes before handing in the lab. If you don't understand what you're doing, come in for help well before the lab is due.
Identify potential sources of scientific error and divide these into 2 columns: random and systematic. Besides listing sources of error, realistic estimates of error magnitude should be made. E.g., if you recognize a lab situation that involves unavoidable parallax, estimate the magnitude of that uncertainty while you're still in the lab. Don't forget the inherent precision of the instruments. Be quantitative wherever possible.
The crown jewel of any lab is NOT a low error result, but rather a determination of whether or not your error is acceptable when considering the uncertainty inherent in that lab. Saying 5% error is good because it's less than 10% is not saying anything at all. Consult the handout on "Error Propagation" for ideas on how to calculate limits of acceptable error.
7. CONCLUSION/SUMMARY - a final analysis of the lab. A word-processed conclusion is preferred but not required. State whether or not you accomplished your purpose and justify this statement with a summary of your results and explanation. Answer any specific questions with self-contained sentences. You are expected to go beyond tersely answering the questions. Think, explore, and look for connections. Discuss the significance of any graphical trends, discontinuities and intercepts. If your error does not fall within the window of acceptable error, explain why. Discuss any insights your lab results give into related topics. This section is pretty much a catch-all for lab related discussion, but such discussion should be meaningful, not just filler to pad out its length.