What does P value in Grubbs test mean?
Grubbs’ test statistic (G) is the difference between the sample mean and either the smallest or largest data value, divided by the standard deviation. Minitab uses Grubbs’ test statistic to calculate the p-value, which is the probability of rejecting the null hypothesis when it is true.
What is G in Grubbs test?
The Grubbs’ test statistic is defined as: G = \frac{\max{|Y_{i} – \bar{Y}|}} {s} with \bar{Y} and s denoting the sample mean and standard deviation, respectively. The Grubbs’ test statistic is the largest absolute deviation from the sample mean in units of the sample standard deviation.
How do I use Grubbs test?
To start the Grubbs test go to the menu Testing outliers / Grubbs test. In the General tab, select the data and the Grubbs test option (the Double Grubbs test can be used to detect two outliers). As an alternative hypothesis choose the two-sided option. The default significance level is left as is: 5%.
Why is Grubbs test important?
Grubbs’ test is used to find a single outlier in a normally distributed data set. The test finds if a minimum value or a maximum value is an outlier.
Does Grubbs test use degrees of freedom?
The Grubbs test statistic is the largest absolute deviation from the sample mean in units of the sample standard deviation. with tα/(2N),N−2 denoting the upper critical value of the t-distribution with N − 2 degrees of freedom and a significance level of α/(2N).
Does Grubbs test require normal distribution?
Definition. Grubbs’s test is based on the assumption of normality. That is, one should first verify that the data can be reasonably approximated by a normal distribution before applying the Grubbs test. Grubbs’s test detects one outlier at a time.
When can you use Grubbs test?
single outlier
Grubbs’ test is used to find a single outlier in a normally distributed data set. The test finds if a minimum value or a maximum value is an outlier. Cautions: The test is only used to find a single outlier in normally distributed data (excluding the potential outlier).
Can Excel do a Grubbs test?
The following screenshot shows how to create a histogram in Excel using the Data Analysis ToolPak: From the histogram, we can see that the data is roughly normally distributed. This means that we can go ahead and conduct Grubbs’ Test.
What does Grubbs test mean?
Grubbs’ test is based on the assumption of normality. That is, one should first verify that the data can be reasonably approximated by a normal distribution before applying the Grubbs’ test. Grubbs’ test detects one outlier at a time.
What is a critical value table?
A “t table” is also known as the “Student’s t Table.”. A critical value is the value that a test value must be greater than to reject the null hypothesis.
How to find critical values in MS Excel?
To find the F critical value in Excel, you can use the F.INV.RT () function, which uses the following syntax: This function returns the critical value from the F distribution based on the significance level, numerator degrees of freedom, and denominator degrees of freedom provided.