Transcript Chapter 12 Sections 4/5

Chapter 12 Sections 4/5
Algebra 2 Notes ~ February 17, 2009
Warm-Ups

Copy the following table:
Right Handed
Left Handed
Right Shoe 1st
Left Shoe 1st
1st One Grabbed
Don’t Know

Ask 10 different people in the class what their dominate hand
is and which shoe they put on first. Fill out the table.

Find each probability:
Chapter 12 Section 4
Standard Deviation
Measures of Variation

Range of a set of data: the difference between the
greatest and least values in the data set

Interquartile Range: the difference between the third
and first quartiles.
Measures of Variation

Thirteen men qualified for the 2002 U.S. Men’s Alpine Ski
Team. Find the range and the interquartile range of their
ages at the time of qualification:
27, 28, 29, 23, 25, 26, 26, 28, 22, 23, 23, 21, 25
STEP 1: Find quartiles 1, 2, 3, and 4 of the data
Standard Deviation




the mean of the data set
n = the number of values in the data set
the difference between each value and the
mean
The symbol
means “sum”
Finding the Standard Deviation

Find the mean and the standard deviation for the values 48.0,
53.2, 52.3, 46.6, 49.9.

First find the mean (

Organize the info into a table:
).
Finding the Standard Deviation

Find the mean and the standard deviation for the
values 50, 60, 70, 80, 80, 90, 100, 110.
Using Standard Deviation

Look at page 670 Example #3; use the table of values of
Daily Energy Demand During August. The mean of these
values is 43.2 and the standard deviation is about 6.0.
Within how many standard deviations of the mean to all
the values fall?
Using Standard Deviation

In May, the mean daily energy demand is 35.8 MWh, with
standard deviation of 3.5 MWh. The power company
prepares for any demand within three standard deviation
of the mean. Are they prepared for a demand of 48
MWh? Explain.
Finding the z-score

Z-score: the number of standard deviations that a value
from the data set is from the mean

A set of values has a mean of 85 and a standard deviation
of 6. Find the z-score of the value 76.

Find the value that has a z-score of 2.5
Chapter 12 Section 5
Working With Samples
Sample Proportions

Sample: gathers information from only part of a
population

Sample Proportion =



x is the number of times an event occurs
n is the sample size
Example: In a sample of 350 teenagers, 294 have never
made a snow sculpture. Find the sample proportion for
those who have never made a snow sculpture.
Sample Proportions
 Two
major factors that influence the
reliability of samples:
1.
Sampling Bias
2.
Sample Sizes
What is “Bias”??
Bias in Sampling

Bias: To show favoritism in a person or thing; to influence
unfairly; prejudice

A news program reports on a proposed school dress code.
The purpose of the program is to find what percent of the
population in its viewing area favors the dress code. Discuss
the bias in the three types of sampling methods.



Viewers are invited to call in and express their preferences
A reporter interviews people on the street near the local high
school
During the program, 300 people are selected at random from the
viewing area. Then each person is contacted.
Comparing Sampling Sizes
 How
would the size of the sample
affect the results??
Using the Margin of Error

The larger the sample size, the smaller the margin of
error

Example: A recent poll reported that 56% of voters
favored President Obama’s Stimulus Plan, with a margin of
error of
. Estimate the number of participants in
the poll.

Use the margin of error to determine the likely range for the
true population proportion
Using the Margin of Error

Example 2: A survey of 2580 students found that 9% are
left-handed.

Find the margin of error for the sample

Use the margin of error to find the interval that is likely
to contain the population proportion
Homework #25
 Pg
672 #1, 2, 4, 5, 8, 15, 21
 Pg
680 #1, 2, 4, 5, 8-10, 12, 13, 16, 18, 20,
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