BIOL2300_chapter 1

# BIOL2300_chapter 1 - CHAPTER 1 Introduction Statistics...

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1 CHAPTER 1: Introduction Statistics refers to the scientific study of numerical data collected from natural phenomena. It provides a set of tools for dealing with quantitative information collected during scientific studies. It typically deals with many measurements, not just a single observation. For example, you are a visiting explorer from Mars, and you ask: How tall is a typical human male? Are human males or females taller? If I give you just one measurement of 1.7 meters for a male, and one measurement of 1.6 meters for a female, have I answered your question? Many scientific questions require analyzing several measurements to come to a definitive answer. When analyzing such data, the basic problem that statistics seeks to address is that of variation . When we make many measurements of the same “thing”, they usually vary, due to measurement errors inherent, “natural” variation Again, suppose you are a visitor from Mars, and you have asked me how tall human males are, and whether males and females differ in height. Being a human being, I know that there is a lot of variation in height among people, both men and women, so I supply this table of data with several measurements: Men Women 1.67 m 1.43 m 1.79 m 1.54 m 1.85 m 1.59 m 1.58 m 1.78 m How do you, the Martian explorer, interpret these data in a way that answers your question? It would be reasonable to take the averages for men and women. How is the average computed? Here are the results

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2 Men : 1.72 m Women : 1.59 m There are a whole lot of questions that arise if you think about this situation even a little bit, such as: How reliable are these numbers, and how reliable is a conclusion that men are taller than women? How “typical” are the estimates that men are 1.72 m tall, and women are 1.59 m tall? Could it just be accidental that I measure 4 men that were taller than the 4 women I measured? How much more reliable might are conclusions be if we measured more people? How many measurements should we make if we want a highly reliable conclusion? All these questions arise because height of human beings is a highly variable quantity. The procedures of statistics help us answer both our underlying scientific questions (how tall are humans and are males and females different) and these additional questions about reliability that arise about the answers to the scientific questions. Nearly all biological quantities show greater or lesser variation, making statistics essential to the study of biology. The earliest developments of statistics took place prior to the 20 th century, by mathematicians attempting to solve problems arising in astronomy and physics. In the late 19 th and 20 th century, biologists became interested in statistics for its ability to describe heredity, that is, resemblance among relatives.
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BIOL2300_chapter 1 - CHAPTER 1 Introduction Statistics...

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