Statistics and Models Section 2.2

1. Statistics and ModelsSection 2.2 Objectives: Explain how scientists use statistics. Describe the types of models commonly used by scientists.

2. Important Statistical Terms • Mean = average • Median – middle number • Mode – most frequent number • 13, 7, 6, 3, 6: Find the mean, median, and mode. • Distribution – the arrangement of the bars in a bar graph of a population • EX: Size Distribution of Dwarf Wedge Mussels (Fig. 9, p.39) • Normal distribution – bell-shaped curve

3. Chapter 2 Section 2 Statistics and Models Size Distribution of Dwarf Wedge Mussels

4. Important Statistical Terms (cont.) • Probability – the chance that something will happen • What does a probability of 0.7 tell you? • Importance of sample size • Sample – a representative group • EX: pennies • Exit Slip: Turn this in! 5 numbers with a mean of 12 Find the mode and the median

5. M&M Samples and Population  • Count your total number of M&M’s. • Count by each color. • Combine all data for your group, and add to data table. • Combine all data for the class, and add to the data table. • At what point did the data match the “normal distribution”?

6. M&M’s Color Distribution

7. Statistics in Everyday Life • “There is a 30% chance of rain today.” • “A study shows that rain levels are 20% below average this year.” • Risk – the probability of an unwanted outcome. • What do you think is the risk of a big oil spill? • The actual biggest cause of oil polluting is ___________.

8. Risk of Being Killed By Lightning • Lightning kills about 80 people each year in the U.S. • The population of the U.S. is about 280 million. (How many 0’s is that?) • What is your chance of being killed by lightning?

9. Models • Physical models • 3-D; can be touched • EX: crash dummies, model airplanes • Graphical models • Maps and charts • Conceptual models • Verbal or graphical explanation of how a system works or is organized • EX: flow chart of the water cycle, atom

10. Chapter 2 Section 2 Statistics and Models Conceptual Model of Mercury Contamination

11. Models (cont.) 4. Mathematical model • Uses equations to represent the way a system or process works • EX: weather models predict rain chances • Exit Slip: Are models always right? Support your answer.