Shapiro Test Error

[dantheman]

Hi All. This is my first post

I want to check for the normality of my data using a Shapiro-Wilk test. It worked fine for all the other variables I have looked at, but suddenly it says "sample size must be between 3 and 5000". I am definitely in this range (n=21).

I have a column of data with 2 land management strategies (text), and a column containing a protein value (numbers). I want to see whether each management type's protein values are normally distributed. Below is the code. I would really appreciate your help with this!

Thanks

Daniel

#csv file name "Mean_Protein

attach(Mean_Protein)
RP.vnp <- Mean_Protein$Management == "VNP" #first management system
RP.konv <- Mean_Protein$Management == "KONV" #second management system

#for the konv management system:
shapiro.test(Mean_Protein$Protein_rel_TM_g_kg[RP.konv])
attach(Mean_Protein)
RP.vnp <- Mean_Protein$Management == "VNP"
RP.konv <- Mean_Protein$Management == "KONV"

shapiro.test(Mean_Protein$Protein_rel_TM_g_kg[RP.konv])

[andresrcs]

Hi!

Since this is most likely related to your specific data, to help us help you, could you please prepare a reproducible example (reprex) illustrating your issue? Please have a look at this guide, to see how to create one:

FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A minimal reproducible example consists of the following items: A minimal dataset, necessary to reproduce the issue The minimal runnable code necessary to reproduce the issue, which can be run on the given dataset, and including the necessary information on the used packages. Let's quickly go over each one of these with examples: Minimal Dataset (Sample Data) You need to provide a data frame that is small enough to be (reasonably) pasted on a post, but big enough to reproduce your issue. Let's say, as an example, that you are working with the iris data frame head(iris) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.…

[dantheman]

Management Systems are either "KONV" or "VNP"

The values are under "Protein_rel_TM_g_kg"

In the CSV file itself, Management is simply showing as "Management", not "I...Management" as in R Studio. I don't know why but perhaps that plays a role here too?

[dantheman]

This is the raw data

Management	Protein_rel_TM_g_kg
KONV	154.3308943
KONV	149.1710395
KONV	138.6193821
KONV	137.1424695
KONV	148.7541504
VNP	134.9632877
VNP	95.34660831
VNP	138.8368989
VNP	149.2707739
VNP	123.6545293
VNP	120.6370481
VNP	120.9075132
VNP	119.3779466
VNP	113.2173484
VNP	106.849136
VNP	122.6948868

[andresrcs]

The information you have provided does not reproduce your issue, please read the guide I linked for you and try to make a proper reproducible example.