Practices of Science: Scientific Error (2024)

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NGSS Science and Engineering Practices

Planning and Carrying Out Investigations

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Practices of Science: Scientific Error

When a single measurement is compared to another single measurement of the same thing, the values are usually not identical. Differences between single measurements are due to error. Errors are differences between observed values and what is true in nature. Error causes results that are inaccurate or misleading and can misrepresent nature.

Scientifically accepted values are scientists’ current best approximations, or descriptions, of nature. As information and technology improves and investigations are refined, repeated, and reinterpreted, scientists’ understanding of nature gets closer to describing what actually exists in nature. However, nature is constantly changing. What was the best quality interpretation of nature at one point in time may be different than what the best scientific description is at another point in time.

Errors are not always due to mistakes. There are two types of errors: random and systematic. Random error occurs due to chance. There is always some variability when a measurement is made. Random error may be caused by slight fluctuations in an instrument, the environment, or the way a measurement is read, that do not cause the same error every time. In order to address random error, scientists utilized replication. Replication is repeating a measurement many times and taking the average.

Systematic error gives measurements that are consistently different from the true value in nature, often due to limitations of either the instruments or the procedure. Systematic error is one form of bias. Many people may think of dishonest researcher behaviors, for example only recording and reporting certain results, when they think of bias. However, it is important to remember that bias can be caused by other factors as well. Bias is often caused by instruments that consistently offset the measured value from the true value, like a scale that always reads 5 grams over the real value.

SF Fig. 1.4. Instrumental error occurs when instruments give inaccurate readings, such as a negative mass reading for the apple on a scale.

Photo by Alyssa Gundersen

Error cannot be completely eliminated, but it can be reduced by being aware of common sources of error and by using thoughtful, careful methods. Common sources of error include instrumental, environmental, procedural, and human. All of these errors can be either random or systematic depending on how they affect the results.

  • Instrumental error happens when the instruments being used are inaccurate, such as a balance that does not work (SF Fig. 1.4). A pH meter that reads 0.5 off or a calculator that rounds incorrectly would be sources of instrument error.
  • Environmental error happens when some factor in the environment, such as an uncommon event, leads to error. For example, if you are trying to measure the mass of an apple on a scale, and your classroom is windy, the wind may cause the scale to read incorrectly.
  • Procedural error occurs when different procedures are used to answer the same question and provide slightly different answers. If two people are rounding, and one rounds down and the other rounds up, this is procedural error.
  • Human error is due to carelessness or to the limitations of human ability. Two types of human error are transcriptional error and estimation error.
    • Transcriptional error occurs when data is recorded or written down incorrectly. Examples of this are when a phone number is copied incorrectly or when a number is skipped when typing data into a computerprogram from a data sheet.
    • Estimation error can occur when reading measurements on some instruments. For example, when reading a ruler you may read the length of a pencil as being 11.4 centimeters (cm), while your friend may read it as 11.3 cm.

Scientists are careful when they design an experiment or make a measurement to reduce the amount of error that might occur.

Question Set

  1. When estimating the area covered by an object, what type of error might you make and what sources might have caused it? Can you do anything to reduce the amount of error that might occur?
  2. What other sources of errors might you need to be aware of when conducting scientific investigations?
  3. How can you reduce error when you design experiments or make a measurement?
Practices of Science: Scientific Error (2024)

FAQs

What is an acceptable scientific error? ›

In some cases, the measurement may be so difficult that a 10 % error or even higher may be acceptable. In other cases, a 1 % error may be too high. Most high school and introductory university instructors will accept a 5 % error. But this is only a guideline.

What are the errors in the scientific method? ›

Common sources of error include instrumental, environmental, procedural, and human. All of these errors can be either random or systematic depending on how they affect the results. Instrumental error happens when the instruments being used are inaccurate, such as a balance that does not work (SF Fig. 1.4).

Are errors acceptable in science? ›

The amount of error that is acceptable depends on the experiment, but a margin of error of 10% is generally considered acceptable. If there is a large margin of error, you'll be asked to go over your procedure and identify any mistakes you may have made or places where error might have been introduced.

What are the three main sources of error? ›

Physical and chemical laboratory experiments include three primary sources of error: systematic error, random error and human error. These sources of errors in lab should be studied well before any further action.

What amount of error is acceptable? ›

The acceptable margin of error usually falls between 4% and 8% at the 95% confidence level.

Is a 7 percent error good? ›

Answer and Explanation:

At the high school level, it's generally acceptable to have 5-10% error for laboratory experiments. College professors generally look for error levels closer to 5%. However, the harder it is to measure, the closer the acceptable error rate gets to 10%.

What are the 3 types of errors in science? ›

The three types of experimental error are systematic, random, and blunders. Systematic errors are errors of precision as all measurements will be off due to things such as miscalibration or background interference. Random errors occur due to happenstance, such as fluctuations in temperature or pH.

What is an example of a bad scientific method? ›

Some examples of bad science include a study in which the wrong data were analyzed[4], a study with mistaken code[5], a study of thymus gland size with bad sampling leading to erroneous conclusions[6], a study with incorrect analyses leading to invalid conclusions[7], et cetera.

What are the biggest scientific blunders? ›

Massive blunders like the invention of nuclear weapons, fossil fuels, CFCs (chlorofluorocarbons), leaded petrol and DDT. And tenuous theories and dubious discoveries like luminiferous aether, the expanding earth, vitalism, blank slate theory, phrenology, and Piltown Man, to name just a few.

How much error is acceptable in research? ›

An acceptable margin of error used by most survey researchers typically falls between 4% and 8% at the 95% confidence level.

How do you correct errors in scientific research? ›

Errors can be identified and corrected with tests of the equipment and programs, examination ofresults, peer review, and replications.

Can the scientific method be wrong? ›

Documentation of experiments is always flawed because everything cannot be recorded. One of the most significant problems with the scientific method is the lack of importance placed on observations that lie outside of the main hypothesis (related to lateral thinking).

What is human error called in science? ›

In science, a blunder is an outright mistake. An individual might record a wrong number, or add a digit when reading a scale, for instance. Although the types of mistakes are similar to systematic and random errors, blunders can be identified because the mistakes are usually not consistent.

What is a random error in science? ›

Random and systematic error are two types of measurement error. Random error is a chance difference between the observed and true values of something (e.g., a researcher misreading a weighing scale records an incorrect measurement).

What are examples of errors in a lab? ›

Examples here could include faulty measurement equipment, inadequate sensitivity of instruments, or calibration errors, which have the result of meaning an experiment becomes 'biased'. The second of these groups are random errors, which are caused by unknown and unpredictable changes in a measurement.

What is an acceptable error rate? ›

What is an acceptable error rate and why is it important? In most firms, the error rate ranges between 10 and 30 errors per hundred opportunities. Failure rates of five to 10 out of every hundred opportunities are possible in well-managed organizations utilizing standard quality management practices.

What is an acceptable standard error? ›

With a 95% confidence level, 95% of all sample means will be expected to lie within a confidence interval of ± 1.96 standard errors of the sample mean. Based on random sampling, the true population parameter is also estimated to lie within this range with 95% confidence.

What is a good standard error for an experiment? ›

Standard error measures the amount of discrepancy that can be expected in a sample estimate compared to the true value in the population. Therefore, the smaller the standard error the better. In fact, a standard error of zero (or close to it) would indicate that the estimated value is exactly the true value.

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