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Observational or Experimental?

Observational or Experimental?. Section 1-6. Two types of studies. Observational – Draw conclusions based on observations of what is happening or what has happened. Example “motorcycle owners are getting older and richer”

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Observational or Experimental?

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  1. Observational or Experimental? Section 1-6

  2. Two types of studies • Observational – Draw conclusions based on observations of what is happening or what has happened. • Example • “motorcycle owners are getting older and richer” • This was based on what a researcher had observed happening to motorcycle owners over a period of time.

  3. Experimental – Tries to determine how the manipulation of one variable influences other variables. • Independent Variables –(Explanatory Variable) - the variable being manipulated by the researcher • Dependent Variables – (Response Variable) – the resultant variable • Confounding Variables – One that influences the dependent variable, but cannot be separated from the independent variable

  4. Ex. Two groups of female students were told to do as many sit-ups as possible in 90 seconds. The first group was told, “Do your best” and the second group was told to “Increase the number each day by 10%.” Results: The first group average 43 per day and the second group averaged 56 per day.Conclusion: Athletes given specific goals perform better.Are there any confounding variables. Identify the dependent variable: Independent variable:

  5. Observational or Experimental The Colorado Division of Wildlife netted and released 774 fish at Quincy Reservoir. There were 219 perch, 315 blue gill, 83 pike, and 157 rainbow trout.

  6. Observational or Experimental • The Colorado Division of Wildlife caught 41 bighorn sheep on Mt. Evans and gave each one an injection to prevent heart worm. A year later, 38 of these sheep did not have heart worm, while the other three did.

  7. Observational or Experimental • The Colorado Division of Wildlife imposed special fishing regulations on the Deckers section of the South Platt River. All trout under 15 inches must be released. A study of trout before and after the regulation went into effect showed the average length increased by 4.2 inches after the new regulation.

  8. Observational or Experimental • An ecology class used binoculars to watch 23 turtles at Lowell Ponds. It was found that 18 were box turtles and five were snapping turtles.

  9. Seconds Holiday BellRinger August 31 "Did you enjoy your holiday?" asked Mrs Jackson. "Yes", replied Mrs White, all 864,789 seconds of it." 1)A day trip to Blackpool 4)A month in Russia 2)Three days in London 5)Two weeks in Florida 3)A week in Pwllheli 6)10 days touring Scotland Which holiday do you think Mrs White enjoyed?

  10. Uses and misuses of Statistics • Stats are helpful in many ways. However another aspect of stats involves the misuse of statistical techniques to • Sell products that don’t work properly • Prove something true that’s not really true • Get our attention by using stats to evoke shock, fear, and outrage Figures don’t lie, but liars figure!

  11. Just because we are presented with the results of a study or poll, it doesn’t mean they are reliable. Sometimes important information is left out so that we can interpret the results incorrectly.

  12. Ways Stats can be Misrepresented • Suspect Samples • Ambiguous Averages • Changing the Subject • Detached Stats • Implied Connections • Misleading Graphs • Faulty Survey Questions

  13. Suspect Samples • A good sample must be • Large enough • Selected the correct way to represent the population • Example 1: “Three out of four doctors surveyed recommend….” - we don’t know how many doctors were actually surveyed • Example 2: A study was conducted using only men – but have been generalized to both men and women.

  14. Ambiguous Averages • Choosing the average that lends the most evidence to support their position • Mean • Median • Mode • Midrange

  15. Changing the Subject • Choosing a different way to say the same thing so that it is more helpful to you or hurtful to an opponent • Ex. A politician states his expenditures as a mere 3%. His opponent states that the expenditure is $6,000,000. Both are the same, but one sounds better than the other.

  16. Detached Statistics • No comparison is made to another study • Ex. “Our brand of crackers has 1/3 fewer calories.” • 1/3 fewer than what? No comparison has been made. • Tylenol works four times faster Always ask yourself – compared to what?!

  17. Implied Connections • Used words to imply something that might not be true. • Ex. “Eating fish may help to reduce your cholesterol” - There is no guarantee. • Ex. “Studies suggest using this machine will reduce your weight. • Ex. “Taking calcium will lower blood pressure in some people” Key words to look for: may, some people, might help

  18. Misleading Graphs • Distorting a visual image 45% unsafe Almost the same number of % safe and unsafe but picture distorts results 55% safe

  19. Faulty Survey Questions • The way in which questions are worded could drastically change results • Ex. “Should T. L. Hanna build a new stadium?” • “Should school taxes be increased so that T. L. Hanna can build a new stadium?”

  20. Homework • Page 29 (1 – 25) • 1 is True • Skip 20 • 21 is ‘random’

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