Transcript Statistics and Models (Section 2.2)

Statistics and Models
Section 2.2
Objectives:
1. Explain how scientists use
statistics.
2. 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
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 
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
Brown (30%)
Red (20%)
Blue (10%)
Orange
(10%)
Green (10%)
Yellow (20%)
# in your % of
# in % of
package total in
class class
package
total
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 models
1. 3-D; can be touched
2. EX: crash dummies, model airplanes
2. Graphical models
1. Maps and charts
3. Conceptual models
1. Verbal or graphical explanation of how a
system works or is organized
2. EX: flow chart of the water cycle, atom
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.