Error That Can Occur In An Experiment
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Sources Of Error In Physics
Incomplete definition (may be systematic or random) - One reason that it is impossible to make exact measurements is that the measurement is not always clearly defined. For example, if two different people measure the length of the same rope, they would probably get different results because each person may stretch the rope with a different tension. The best way to minimize definition errors is to carefully consider and specify the conditions that could affect the measurement. Failure to account for a factor (usually systematic) - The most challenging part of designing an experiment is trying to control or account for all possible factors except the one independent variable that is being analyzed. For instance, you may inadvertently ignore air resistance when measuring free-fall acceleration, or you may fail to account for the effect of the Earth's magnetic field when measuring the field of a small magnet. The best way to account for these sources of error is to brainstorm with your peers about all the factors that could possibly affect your result. This brainstorm should be done before beginning the experiment so that arrangements can be made to account for the confounding factors before taking data. Sometimes a correction can be applied to a result after taking data, but this is inefficient
the measurement devices (hard to read scales, etc.) - Usually caused by poorly or miscalibrated instruments. - There are usually ways to determine or estimate. - Cannot reduce by repeated measurements, but can account for in some way. 3. Indeterminate (Random)
Examples Of Experimental Errors
Errors
- Natural variations in measurements. - May be result of operator bias, sources of error in a biology lab variation in experimental conditions, or other factors not easily accounted for. - May be minimized by repeated measurement and using an average value. source of error definition Experimental results may be described in terms of precision and accuracy. Precision - relatively low indeterminate error. - reproducibility. - high precision means a number of readings or trials result in values close to the same https://answers.yahoo.com/question/index?qid=20090707145338AAaUiOa number. Accuracy - relatively low determinate error. - close to a true value. Accurate and precise Precise but not accurate Reliability- a procedure is said to be reliable if it may be completed with a high degree of accuracy and precision. For most of our investigations we will be concerned with the precision of results. Experimental Data and Measures of Uncertainty Quantities that give some measure of experimental precision are Deviation (individual values) Average http://www.ahsd.org/science/stroyan/hphys/stats/meas_uncert_1.htm deviation Average Deviation of the Mean (Standard Average Deviation) Sample standard deviation (sometimes denoted as ) Standard error It is customary to report experimental results with an uncertainty in the following form Result = Average ± uncertainty The uncertainty is one of the measures of precision given above (a.d., A.D., s, or Sx). For our present cases we will use standard error and report results as Result = Average ± Sx This information is simply preliminary to analyses we will be performing on some sample data, and data we will collect in the future. The idea here is to give you the formulae that are used to describe the precision of a set of data. We will see a bit more later. We need to see a calculation of these quantities. These pages illustrate one run through of calculations Another document will be about what these statistical quantities might tell us and how we might use this information to make certain decisions (usually as concerns elimination of data.) Reading Instruments and Errors Recorded values should reflect the precision of an instrument. Recorded values should have at least one more place than the smallest division on the scale of the instrument. Readings from a meter stick with major divisions (numbered divisions) of cm, that has each mm marked, would be reported to 0.01cm. Estimated uncertainty in a single measureof this type result in measured values that are consistently too high or consistently too low. Systematic errors may be of four kinds: 1. http://www.physics.nmsu.edu/research/lab110g/html/ERRORS.html Instrumental. For example, a poorly calibrated instrument such as a thermometer https://www.reference.com/science/possible-sources-errors-lab-5937a6475f2cd221 that reads 102 oC when immersed in boiling water and 2 oC when immersed in ice water at atmospheric pressure. Such a thermometer would result in measured values that are consistently too high. 2. Observational. For example, parallax in reading a meter scale. 3. of error Environmental. For example, an electrical power ìbrown outî that causes measured currents to be consistently too low. 4. Theoretical. Due to simplification of the model system or approximations in the equations describing it. For example, if your theory says that the temperature of the surrounding will not affect the readings taken when it actually does, then sources of error this factor will introduce a source of error. Random Errors Random errors are positive and negative fluctuations that cause about one-half of the measurements to be too high and one-half to be too low. Sources of random errors cannot always be identified. Possible sources of random errors are as follows: 1. Observational. For example, errors in judgment of an observer when reading the scale of a measuring device to the smallest division. 2. Environmental. For example, unpredictable fluctuations in line voltage, temperature, or mechanical vibrations of equipment. Random errors, unlike systematic errors, can often be quantified by statistical analysis, therefore, the effects of random errors on the quantity or physical law under investigation can often be determined. Example to distinguish between systematic and random errors is suppose that you use a stop watch to measure the time required for ten oscillations of a pendulum. One source of error will be your reaction time in starting and stopping the watch. During one measurement you may star
Celebrations Home & Garden Math Pets & Animals Science Sports & Active Lifestyle Technology Vehicles World View www.reference.com Science Chemistry Chem Lab Q: What are some possible sources of errors in the lab? A: Quick Answer Some possible sources of errors in the lab includes instrumental or observational errors. Environmental errors can also occur inside the lab. Continue Reading Keep Learning What are sources of error in a chemistry lab? What are some sources of error in synthesis of alum from aluminum foil? How do you perform acid-base titration in a lab? Full Answer Instrumental errors can occur when the tools are not functioning exactly as they should be. An example of this error is a thermometer used to measure temperature. If the thermometer is not calibrated correctly, it can cause an error. An observational error example would be if the experimenter did not read the thermometer correctly when recording results. An example of an environmental error is when an air conditioner in a room causes the table to vibrate slightly and this vibration causes the measurement to be slightly off. Learn more about Chem Lab Sources: nmsu.edu columbia.edu Related Questions Q: What is an example of a lab write up? A: A lab write up is a report explaining a scientific experiment and its results. A standard lab write up includes the following sections: I. Introduction/Pur... Full Answer > Filed Under: Chem Lab Q: What is an esterification lab? A: An esterification lab creates esters from the reaction between alcohols and carboxylic acids. Esters are commonly used as fragrances in things like perfume... Full Answer > Filed Under: Chem Lab Q: How do you interpret lab test results? A: Lab test results may be positive, negative or inconclusive, states WebMD. There are also what are called āfalse-positiveā and āfalse negativeā test results... Full Answer > Filed Under: Chem Lab Q: What is a clamp holder used for in a lab? A: The clamp holder is used in conjunction with several other lab pieces to hold a container of any given substance during an experiment that often involves h... Full Answer > Filed Under: Chem Lab You May Also Like Q: How do you grow salt crystals? Q: What are the main sources of the U.K. constitution? Q: What is chromium-vanadium steel? Q: How do you calculate relative error? Q: What are so