You want to assess the attitudes towards math by the students in your school district. you first divide the district into groups, in this case the twenty different high schools. we then randomly select five of the schools. this would conclude the first stage. in each school we then have natural groups of students (each math class would represent a group). so we randomly select five classes from each school. these are the students who we will sample. this is an example of what type of sample?

imperial crisis leads to civil war.

roman forces withdraw from britain as goths attack rome.

odoacer topples romulus augustus

huns attack the empire and drive german peoples ahead of them.

the arab empire adopted the muslim religion as their main belief. arabs would influence the people from the territories they invaded towards islam (the muslim belief).

nevertheless, throughout the history of the arab empire, rulers brought intellectual individuals from other religions to their centers of learning. these other foreigners included jews, christians, greeks, persians, and indians.   these resulted in the adoption of important knowledge developed by these cultures by the arabic empire. for example, the works of aristotle were translated from greek to arab and indian scientists brought the numerical concept of "zero" to the arabs.

nowadays, 93% of the arab population is muslim, which at the same time is subdivided in sects including the sunni, zaini, alawi, shia. the remaining 7% is composed mainly of christians.