Final answer:
The null hypothesis (H0) typically states that there is no effect or no difference, and in this case, it would state that the average petal length of an iris flower does not vary by its species. The alternative hypothesis (HA) is that the average petal length varies by species. An ANOVA test can be used to determine if this difference is statistically significant.
Step-by-step explanation:
You are conducting research on the average petal lengths for various species of iris flowers. When accessing the iris dataset using attach(iris) in R, several hypothesis tests can be proposed based on the question of interest. In this case, the null hypothesis (H0) and alternative hypothesis (HA) are set up for statistical testing.
- H0: The average petal length of an iris flower does not vary by its species.
- HA: The average petal length of an iris flower varies by its species.
This forms a typical null and alternative hypothesis pair for an ANOVA test, where we would test if there are significant differences in petal lengths across the different species of iris. When you perform the ANOVA test on the iris dataset, it will allow you to see if there's enough evidence to reject the null hypothesis and conclude that the average petal length varies according to species.