The word "do" is a verb. The word "does" is used for the third person singular present tense. For example, "I do not know her name" but "he does not know her name".
Within group differences refers to differences within one individual group. Between group differences refers to the differences between 2 or more groups.
Genetic differences
What are the differences between polycarbohydrate and polysaccharide?
differences between now and then 1905s
differences between errors and frauds
differences between Hausa and Yoruba
what are the differences between indus and sumer civilization
Differences between Classification and Tabulation
differences between equator and prime meridian
What are some differences between soldiers and Militias
differences between people and cultures
They are to many differences between them