Statistics and ModelsSection 2.2

Objectives:

1. Explain how scientists use statistics.

2. Describe the types of models commonly used by scientists.

Important Statistical Terms

Mean = averageMedian – middle numberMode – most frequent number13, 7, 6, 3, 6: Find the mean, median,

and mode.Distribution – the arrangement of the

bars in a bar graph of a populationEX: 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

Important Statistical Terms (cont.)

Probability – the chance that something will happenWhat does a probability of 0.7 tell you?Importance of sample size

Sample – a representative groupEX: pennies

Exit Slip: Turn this in!5 numbers with a mean of 12

Find the mode and the median

M&M Samples and Population

1. Count your total number of M&M’s.

2. Count by each color.

3. Combine all data for your group, and add to data table.

4. Combine all data for the class, and add to the data table.

5. At what point did the data match the “normal distribution”?

M&M’s Color Distribution

Color # 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

1. Physical models1. 3-D; can be touched

2. EX: crash dummies, model airplanes

2. Graphical models1. Maps and charts

3. Conceptual models1. Verbal or graphical explanation of how a

system works or is organized

2. EX: flow chart of the water cycle, atom

Conceptual Model of Mercury Contamination

Chapter 2 Section 2 Statistics and Models

Models (cont.)

4. Mathematical modelUses equations to represent the way a

system or process worksEX: weather models predict rain chances

Exit Slip: Are models always right? Support your answer.