<Tr> <Td> 45 </Td> <Td> 15 </Td> <Td> 9200 </Td> <Td> 613 </Td> </Tr> <Tr> <Td> 60 </Td> <Td> 30 </Td> <Td> 6461 </Td> <Td> 215 </Td> </Tr> <Tr> <Td> 90 </Td> <Td> 60 </Td> <Td> 3435 </Td> <Td> 57 </Td> </Tr> <P> This histogram shows the number of cases per unit interval as the height of each block, so that the area of each block is equal to the number of people in the survey who fall into its category . The area under the curve represents the total number of cases (124 million). This type of histogram shows absolute numbers, with Q in thousands . </P>

What is the difference between a frequency histogram and a relative frequency histigram