<Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> A population pyramid, also called an "age - sex pyramid", is a graphical illustration that shows the distribution of various age groups in a population (typically that of a country or region of the world), which forms the shape of a pyramid when the population is growing . This tool can be used to visualize and age of a particular population . It is also used in ecology to determine the overall age distribution of a population; an indication of the reproductive capabilities and likelihood of the continuation of a species . </P> <P> Population pyramids often contain continuous stacked - histogram bars, making it a horizontal bar diagram . The population size is depicted on the x-axis (horizontal) while the age - groups are represented on the y - axis (vertical). The size of the population can either be measured as a percentage of the total population or by raw number . Males are conventionally shown on the left and females on the right . Population pyramids are often viewed as the most effective way to graphically depict the age and distribution of a population, partly because of the very clear image these pyramids represent. A great deal of information about the population broken down by age and sex can be read from a population pyramid, and this can shed light on the extent of development and other aspects of the population . </P> <P> The measures of central tendency, mean, median, and mode, should be considered when assessing a population pyramid . since the data is not completely accurate . For example, the average age could be used to determine the type of population in a particular region . A population with an average age of 15 would have a young population compared to a population that has an average age of 55, which would be considered an older population . It is also important to consider these measures because the collected data is not completely accurate . The mid-year population is often used in calculations to account for the number of births and deaths that occur . </P>

What are the main features of a population pyramid
find me the text answering this question