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Causes and Effects Help (page 3)

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By — McGraw-Hill Professional
Updated on Sep 12, 2011

Multiple factors cause both X and Y

If you watch television shows where the advertising is aimed at middle-aged and older folks, you'll hear all about cholesterol and heart disease – probably a good deal more than you want to hear. High cholesterol, low cholesterol, HDL, LDL, big particles, small particles. You might start wondering whether you should go to a chemistry lab rather than a kitchen to prepare your food. The cause-and-effect relationship between cholesterol and heart disease is complicated. The more we learn, it appears, the less we know.

Let's introduce and identify three new friends: factors S, H, and E. Factor S is named ''Stress'' (in the sense of anxiety and frustration), factor H is named ''Heredity'' (in the sense of genetic background), and factor E is named ''Exercise'' (in the sense of physical activity). Over the past several decades, cause-and-effect relationships have been suggested between each of these factors and blood cholesterol, and between each of these factors and the frequency of heart attacks. Figure 7-6 illustrates this sort of ''cause-and-effect web.'' Proving the validity of each link – for example, whether or not stress, all by itself, can influence cholesterol in the blood – is a task for future researchers. But all of the links shown in the diagram have been suggested by somebody.

Causes and Effects

Coincidence

The existence of correlation between two phenomena doesn't necessarily imply any particular cause-and-effect scenario. Two phenomena can be correlated because of a sheer coincidence. This is most likely to happen when the amount of data obtained is not adequate. In the case of blood cholesterol versus the frequency of heart attacks, test populations have traditionally contained thousands of elements (people). The researchers are justified in their conclusions that such correlation is not the product of coincidence. It is reasonable to suppose that some cause-and-effect interaction exists. Researchers are still busy figuring out exactly how it all works, and if they ever get it completely unraveled, it's a good bet that an illustration of the ''cause-and-effect web'' will look a lot more complicated than Fig. 7-6.

Causes and Effects

Correlation indicates that things take place more or less in concert with one another. This allows us to predict certain future events with varying degrees of accuracy. But there is another form of order that can be found in nature. This form of order, defined by a new science called chaos theory, illustrates that some phenomena, totally unpredictable and which defy statistical analysis in the short term or on a small scale, can nevertheless be highly ordered and predictable on a large scale. In a moment, we'll look at this.

Causes and Effects Practice Problems

Practice 1

What are some reasonable cause-and-effect relationships that might exist in Fig. 7-6, other than those shown or those directly between X and Y? Use arrows to show cause and effect, and use the abbreviations shown.

Solution 1

Consider the following. Think about how you might conduct statistical experiments to check the validity of these notions, and to determine the extent of the correlation.

  • H → S (Hypothesis: Some people are born more stress-prone than others.)
  • H → D (Hypothesis: People of different genetic backgrounds have developed cultures where the diets are dramatically different.)
  • E → S (Hypothesis: Exercise can relieve or reduce stress.)
  • E → D (Hypothesis: Extreme physical activity makes people eat more food, particularly carbohydrates, because they need more.)
  • D → S (Hypothesis: Bad nutritional habits can worsen stress. Consider a hard-working person who lives on coffee and potato chips, versus a hard-working person who eats mainly fish, fruits, vegetables, and whole grains.)
  • D → E (Hypothesis: People with good nutritional habits get more exercise than people with bad nutritional habits.)

Practice 2

What are some cause-and-effect relationships in the diagram of Fig. 7-6 that are questionable or absurd?

Solution 2

Consider the following. Think about how you might conduct statistical experiments to find out whether or not the first three of these might be moved into the preceding category.

  • H → E (Question: Do people of certain genetic backgrounds naturally get more physical exercise than people of other genetic backgrounds?)
  • S → E (Question: Can stress motivate some types of people to exercise more, yet motivate others to exercise less?)
  • S → D (Question: Do certain types of people eat more under stress, while others eat less?)
  • S → H (Obviously absurd. Stress can't affect a person's heredity!)
  • E → H (Obviously absurd. Exercise can't affect a person's heredity!)
  • D → H (Obviously absurd. Dietary habits can't affect a person's heredity!)

Practice problems for these concepts can be found at:

Correlation, Causation, Order, and Chaos Practice Test

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