Name: grubbs test for spotting data outliers
Uploaded: 2024-04-04T10:51:12.000Z
Duration: 1 min 2 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.2

CHEM.2.C

quantifying-and-rejecting-outliers-the-grubbs-test

Quantifying and Rejecting Outliers: The Grubbs Test

Il test di Grubbs, come il Q-test di Dixon, è un test statistico per identificare i valori anomali nei dati con una distribuzione normale. In questo caso, il numero di osservazioni dovrebbe essere uguale o superiore a sette.
Per un dato set di dati, questo test prevede il calcolo della statistica G di Grubbs, che è il rapporto tra la differenza assoluta tra il valore discutibile e il valore medio e la deviazione standard del campione.
Il valore G calcolato viene quindi confrontato con il valore critico tabulato di G per un dato livello di confidenza e il numero di osservazioni.
Se il valore G calcolato supera il valore critico di G, l'osservazione discutibile viene considerata un'anomalia dei dati e rifiutata. 
In alternativa, se il valore G calcolato è inferiore al valore critico di G, i dati mantengono l'osservazione discutibile.

quantificare e rifiutare i valori anomali: il test di grubbs

A volte, un set di dati può avere un'osservazione numerica registrata che si discosta notevolmente dal resto dei dati. Supponendo che i dati siano distribuiti normalmente, è possibile utilizzare un metodo statistico chiamato test di Grubbs per determinare se l'osservazione è veramente un valore anomalo. Per eseguire un test di Grubbs a due code, calcolare innanzitutto la differenza assoluta tra il valore anomalo e la media. Quindi, calcola il rapporto tra questa differenza e la deviazione standard del campione. Questo numero è noto come statistica di Grubbs, "G." Quando il valore G calcolato supera il valore critico G per un dato livello di confidenza e il numero di osservazioni, l'osservazione discutibile viene considerata un valore anomalo e rimossa dal set di dati. Al contrario, se il valore G calcolato è inferiore al valore G critico, l’osservazione discutibile non viene considerata un valore anomalo e quindi mantenuta nel set di dati.

Quantificare e rifiutare i valori anomali: il test di Grubbs

Il test di Grubbs, come il Q-test di Dixon, è un test statistico per identificare i valori anomali nei dati con una distribuzione normale. Qui, il numero di ...

Education

Didattica

JoVE Core

Analytical Chemistry

Chimica Analitica

Unit 1

Unità 1

Chemical Applications of Statistical Analyses

Applicazioni chimiche delle analisi statistiche

chemical-applications-of-statistical-analyses

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

grubbs test for spotting data outliers

The Grubbs test is a statistical way to spot a possible outlier in a data set. It is used when the data is assumed to follow a normal distribution. A Grubbs test helps decide whether one unusual numerical value should be treated as a true outlier.

To run a two-tailed Grubbs test, first find the absolute difference between the questionable value and the mean. Then divide that difference by the sample standard deviation. The result is the Grubbs statistic, or G.

Next, compare the calculated G value with the G critical value for the chosen confidence level and the number of observations. If the calculated G is larger, the questionable value is considered an outlier and removed from the data set. If the calculated G is smaller, the value is not considered an outlier and is kept in the data set.

Grubbs Test for Spotting Data Outliers

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The Grubbs test is a statistical way to spot a possible outlier in a data set. It is used when the data is assumed to follow a normal distribution. A Grubbs test helps decide whether one unusual numerical value should be treated as a true outlier. To run a two-tailed Grubbs test, first find the absolute difference between the questionable value and the mean. Then divide that difference by the sample standard deviation. The result is the Grubbs statistic, or G. Next, compare the calculated G...

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key terms and concepts

Learn how the Grubbs test checks a normal data set for a possible outlier by comparing the G statistic with the critical value.

Grubbs Test for Spotting Data Outliers | JoVE K12

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Grubbs Test for Spotting Data Outliers

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