Based on a study she read (Serpell, 1991) and her own personal observations, Lucy believes pet owners experience fewer minor health problems than non-pet owners do. She decides to examine samples of pet owners and non-pet owners and compare how many colds, on average, each group experiences during a 6-month period (October to March). What is Lucy's null hypothesis?

Lucy's null hypothesis is problems of minor health problem is very less in those who have pet and vice versa with non-pet owners.

Explanation:

Hypothesis is a presumption or assuming something. It has two types. One is null hypothesis and another one is alternative hypothesis. When a researcher's presumption proves right that means null hypothesis get accepted and if not that means it is indicating some different result which requires more research. That is alternative hypothesis.

After determining hypothesis it requires some scientific testing. There are number of test. Student's t test, F test etc. On the basis of that finally the result established universally.