Psychology; Hypothesis

eating greasy food causes pimples

this is not a really good hypothesis because by doing research I found out that there are other ways to get pimples. hormone levels, stress, sun exposure, exercise, or any other variables which may conceivably affect your skin. if you eat a hamburger or some chicken can you honestly say that the grease is what caused your pimples? the answer is no everybody reacts to things differently and that's a fact so correctly I would rephrase it to "getting pimples is unaffected by eating greasy food".
 {Archival research}

Null hypothesis
every rose has the same number of petals