The null hypothesis is a general statement or default position that there is no relationship between two measured phenomena, or no association among groups. In your case, the null hypothesis is that there is no relationship between the average age when infants start crawling and the weather temperature. However, there seems to be a slight misunderstanding in your null hypothesis notation. The null hypothesis should be denoted as H0: r = 0, not H0: r 0. Here's why: H0: r = 0 means that there is no correlation between the two variables, which is the essence of a null hypothesis. H0: r 0 would mean that there is some correlation (either positive or negative) between the two variables, which is contrary to the concept of a null hypothesis. Correct Null Hypothesis So, the correct null hypothesis for your scenario should be: H0: r = 0 This means that there is no correlation between the average age when infants start crawling and the weather temperature. Alternative Hypothesis The alternative hypothesis (H1 or Ha) is the statement that directly contradicts the null hypothesis. In your case, the alternative hypothesis would be that there is a correlation between the average age when infants start crawling and the weather temperature. This can be denoted as: Ha: r 0 This means that there is a correlation (either positive or negative) between the average age when infants start crawling and the weather temperature