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

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

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

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

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”?

M&M’s Color Distribution # in your package % of total in package # in class % of class total Brown (30%) Red (20%) Blue (10%) Orange (10%) Green (10%) Yellow (20%)

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 ___________.

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?

Models Physical models Graphical models Conceptual 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

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

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.