1
$\begingroup$

I have a simple dataset on reproductive success of a certain plant species. Reproductive success was defined as a proportion between number of flowers and number of fruits. We measured on 10 different sites, several seasons. I would like to test if there is a significant difference in RS between sites. An example of my dataset:

enter image description here

I used Fisher's exact test - the same approach as in this example here: Fisher's exact test in R - 2x4 table - as follows:

> data <- matrix (c(6, 148, 0, 3, 0, 1, 0, 4, 2, 8, 0, 17, 8, 151, 11, 108, 1, 33, 0, 2), nrow = 10, byrow = T)
> row.names(data) <- c("1","2","3","4","5","6","7","8","9","10")
> colnames(data) <- c("fruit YES", "fruit NO")
> data
   fruit YES fruit NO
1          6      148
2          0        3
3          0        1
4          0        4
5          2        8
6          0       17
7          8      151
8         11      108
9          1       33
10         0        2
> fisher.test(data)

    Fisher's Exact Test for Count Data

data:  data
p-value = 0.3329
alternative hypothesis: two.sided

The result shows that there is no significant difference between sites, but if you check site no. 5 in the data, the percentage of fruit is much higher than the rest. Did I use the right test? If I did - did I do it right? Would you suggest any other method? Additional question: I would also like to check if the number of flowers and pH affect the production of fruits on each site. Which test/method should I use in this case - logistic regression? I'm very new to R, so a more detailed explanation would be very very appreciated. Thank you in advance!

$\endgroup$
0
$\begingroup$

The result shows that there is no significant difference between sites, but if you check site no. 5 in the data, the percentage of fruit is much higher than the rest.

True, however, you have only 2 "yes" and 8 "no", that is why the difference is not significant.

Did I use the right test? If I did - did I do it right? Would you suggest any other method?

The Fisher exact test is appropriate for your data and I have no suggestion of alternatives. Since I'm not an expert in R I can't tell if it was correctly applied.

Additional question: I would also like to check if the number of flowers and pH affect the production of fruits on each site. Which test/method should I use in this case - logistic regression? [...]

Yes, the logistic regression is appropriate, considering that the fruit variable is dichotomous (yes/no). As independent variables you should consider the site as nominal, using the first or the seventh category as reference, and the pH as continuous variable.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.