The meaning of systematic error versus accidental error

Systematic error. systematic error) in repeatability.

condition, the average of the results obtained from an infinite number of measurements of the same measurement.

The difference from the true value being measured.

Systematic error is a kind of error caused by some fixed reasons in the analysis process, which is repeatable, unidirectional, and measurable. That is, under the same conditions, the repeated measurement will be repeated, so that the measurement results are high or low, and the value size also has a certain rule.

Random error. Also known as accidental error.

and indefinite error is a mutually compensating error formed by a series of small random fluctuations of relevant factors in the measurement process. The reason for this is the influence of various unstable random factors in the analysis process, such as room temperature and relative humidity.

and instability of environmental conditions such as air pressure, small differences in analyst operation, and instability of the instrument.

It can be understood in this way: systematic error is due to the deviation of the measurement tool, or other environmental factors, which is always biased in one direction relative to the true value; The accidental error is due to the error between the reading value and the true value caused by the reading or other times, which may be large or small around the true value.

P.S. Definitions of two types of errors.

Systematic error: A holding constant or its variation is part of a predictable measurement error over the course of multiple measurements being measured.

Accidental error: The measurement error in the series of measured values under the same measurement conditions is indefinite, but obeys a certain statistical law.

Definition from Encyclopedia).

The former is inherent and always in one direction, always on the large side or always on the small side. It is not possible to eliminate the average after multiple measurements.

The latter is random, accidental, and can be both greater than or less than the actual value. It can be eliminated on average after multiple measurements.

The main differences are that the properties are different, the causes are different, and the characteristics are different, as follows:

First, the nature is different.

1. Accidental error.

Accidental error generally refers to random error, which is a mutually compensating error formed by a series of small random fluctuations of relevant factors in the measurement process.

2. Systematic error.

Systematic error refers to a non-random error, the difference between the average value of the result obtained by an infinite number of measurements of the same measurement and the true value of the measured under repeatability conditions.

Second, the causes are different.

1. Accidental error.

The reason for this is the influence of various unstable random factors in the analysis process, such as the instability of environmental conditions such as room temperature, relative humidity and air pressure, the small differences in the operation of the analyst, and the instability of the instrument.

2. Systematic error.

The main reasons are:

1) The samples taken do not meet the research tasks.

2) Ignorance of the nature of the population distribution has chosen a sampling procedure that may misinterpret the population distribution.

3) Consciously select the most convenient and problem-solving overall elements, but these elements do not represent the population (e.g., only sampling advanced enterprises).

Third, the characteristics are different.

1. Accidental error.

The size and orientation are not fixed.

2. Systematic error.

Repeatability, unidirectionality, measurability.

The People's Education Publishing House, June 2003, the 7th edition of the full-time ordinary senior high school textbook (compulsory) Physics Volume 1, page 137 on the "error and significant figures" part about the error: from the point of view, the error can be divided into two types: systematic error and accidental error. ”

Systematic errors are caused by the inaccuracy of the instrument itself, or the rough experimental method, or the imperfect experimental principle. The characteristic of systematic error is that when the same experiment is redone many times, the error is always the same large or small, and there will be no situation where this time is too large and the other time is small. In order to reduce the systematic error, it is necessary to calibrate the measuring instrument, improve the experimental method, and design the experiment that is more complete in principle.

Accidental error is caused by the influence of various accidental factors on the experimenter, the measuring instrument, and the measured physical quantity. Accidental errors are always sometimes large and sometimes small, and the probability of being too large or too small is the same. As a result, it is possible to take several more measurements to find the average of the values that have been measured several times, which is closer to the true value than the values measured in one time. ”

Accidental error is also known as random error, and the main differences from systematic error are as follows:

First, the causes are different.

1. Random error: the reason for this is the influence of various unstable random factors in the analysis process, such as the instability of environmental conditions such as room temperature, relative humidity and air pressure.

2. Systematic error: the samples taken do not meet the research task; Lack of understanding of the nature of the population distribution and selection of sampling procedures that may misinterpret the population distribution; Consciously select the most convenient and problem-solving aggregate elements, but these elements are not representative of the population (e.g., sampling only advanced firms).

Second, the meaning of the expression is different.

1. Random error: It is a mutually compensating error formed by a series of small random fluctuations of relevant factors in the measurement process.

2. Systematic error: refers to a non-random error. For example, bias error that violates the principle of randomness, error caused by registration records in sampling, etc.

Third, the characteristics are different.

1. Random error: its absolute value and symbol are unpredictable.

2. Systematic error: repeatability, unidirectionality, and measurability.

Systematic error, also known as definable error, is an error caused by a certain reason, generally with a fixed direction (positive or negative) and magnitude, and is repeated when the measurement is repeated.

According to the error, the systematic error can be divided into method error, instrument error, reagent error and operation error.

1) Method error.

Method errors are caused by imperfect or inappropriate selection of the analytical method itself. For example, errors caused by factors such as precipitation dissolution, co-precipitation, precipitation and decomposition in gravimetric analysis; Errors caused by incomplete titration reactions, the influence of interfering ions, inappropriate indicators, and the occurrence of other side reactions in volume analysis.

2) Reagent error.

Reagent error is an error caused by the reagent not meeting the requirements, such as impure reagent. Reagent errors can be overcome by replacing reagentsThe learning and education network collects and sorts, and the size of the error can also be measured and corrected through blank tests.

3) Instrument error.

Instrument error is an error caused by the inaccuracy of the instrument. For example, the low sensitivity of the balance, the inaccurate weight of the weight itself, the inaccurate scale of burettes, volumetric flasks, pipettes, etc. Therefore, the instrument should be calibrated before using the instrument, and the instrument that meets the requirements should be selected; Or find its correction value and calibrate the measurement results.

4) Operational error.

Errors caused by the analyst's operation not meeting the requirements are called operational errors. For example, the examiner has made an error in the color change of the titration endpoint or has not followed the instructions for the use of the instrumentErrors caused by the collection, collation, and operation of the learning and education network.

Accidental error is characterized by its randomness. If we only measure some physical quantities once, their values may be larger than the true value or smaller than the true value, which is completely accidental, and the cause of the accidental error cannot be controlled, so the accidental error always exists, and the accidental error can be reduced by averaging it through multiple measurements, but it cannot be eliminated.

Since it is an error, it cannot be eliminated, and it can only be improved by doing many tests to reduce the error.

"In a nutshell, accidental error is an error caused by subjective factors, and systematic error is an error caused by objective factors. Systematic errors are unavoidable (but can be reduced by balancing friction, for example), while human errors can be avoided by multiple measurements. ”

Experimental errors revealed from multiple measurements are called accidental errors.

Experimental errors that cannot be revealed from multiple measurements are called systematic errors, and accidental errors are characterized by their randomness.

There is a certain pattern of systematic error.

Accidental error refers to the error caused by measurement or calculation, which can be avoided.

Systematic error refers to the error caused by the experimental instrument or accuracy, etc., which is inevitable.

Systematic errors: Errors that are unavoidable during experiments, such as frictional resistance, air resistance, and errors in the experiment itself, such as unconstant voltage, when a power supply is used.

Accidental errors: Measurement errors, experimental errors, and other man-made, avoidable errors.

To sum up, systematic error is inevitable (but can be reduced by balancing friction, for example), while human error can be avoided by multiple measurements.

What are the two types of errors? What are the basic characteristics of accidental error?

Accidental and systematic errors.

These include: (1) boundedness; (2) symmetry; (3) compensatory; (4) Intensiveness.

The accidental error you are talking about should be random error, random error has always existed, he has randomness, but according to statistical data, the average of the overall random error should be 0, that is, he has positive error and negative error, and the general random error cannot be compensated, nor does it need to be compensated, so we generally don't care about random error. The systematic error is often due to the inaccuracy of the system, and it is relatively fixed over a period of time, so the systematic error can be separated after many tests and compensated in the results, so the systematic error can be compensated. To sum up, the characteristics of accidental error are:

Randomness, unpredictability, non-compensability, and inevitability that always exists in various systems.