Do all studies have hypothesis?
From PsychWiki - A Collaborative Psychology Wiki
While a hypothesis is a specific statement about a prediction in a research study, some studies do not necessarily have a hypothesis such as studies that are designed to be exploratory. There is no formal hypothesis, and the purpose of the study may be to explore some area more thoroughly to develop some specific hypothesis or prediction that can be tested in future research.
Example / Application
Example: Stephen Colbert's Fancy Feast study
Application: The study is done to see if people can distinguish pate from dog food and the results show that most people cannot. The research is more of an observational study as it doesn't hypothesize if one group will distinguish the food more than another or make a prediction as to whether something occurred during the study.The study only observed that the participants where not able to discern dog food from pate.