Making Predictions about a Population

Making Predictions about a Population

7.6G

Learning Objective

TLW will solve problems using data represented in bar graphs, dot plots and circle graphs.

Vocabulary

• Statistics deal with collecting, organizing and interpreting data.

• A survey is a method of collecting information.

Vocabulary

• The group being studied is the population. Sometimes a population can be really large.

• To save time and money, part of the group, called a sample is surveyed

Multiple Choice

What is statistics?

• A method of collecting information.

• The group being studied

• Collecting, organizing and interpreting data

• Part of the group

Multiple Choice

What's the difference between sample and population?

• Sample - the group being studied

  
  

  Population- part of the group

• Sample-part of the group

  
  

  Population- the group being studied

Making Predictions using Ratios

• Remember you can write a ratio using the word to " 2 to 7", a colon " 2 : 7" or a fraction bar " $\frac{2}{7}$  "

P(theme park)

•  $\frac{theme\ park\ photos}{total\ photos}$  

• There's 11 theme park photos and 28 photos total. 

• So the probability of a theme park photo is  $\frac{11}{28}$  .

• Let s represent the number to theme park photos.

• Set up proportion $\frac{11}{28}=\frac{s}{560}$  

• Butterfly method  $28\cdot s\ =11\cdot560$  

• Divide both sides by the coefficient $\frac{28s}{28}\ =\ \frac{6,160}{28}$  

•  $s=\ 220$  

• Of the 560 students you can expect 220 to bring theme park photos.

Multiple Choice

A survey found that 6 out of every 10 students have a blog.

**What is the probability that a student at the school has a blog?

• $\frac{2}{5}$

• $\frac{3}{5}$

Multiple Choice

A survey found that 6 out of every 10 students have a blog.

**Suppose there are about 250 students at the school. About how many has a blog?

• 150

• 100

Making Predictions using Equations

You can also use the percent equation to make predictions.

• Words: What number of students is 85% of 2,450 students?

• Variable: Let n represent the number of students.

• Equation:  $n=0.85\ \cdot2,450$  

• Multiply  $0.85\ \cdot2,450$  

•  $n=\ 2,082.5$  

• About 2,083 students use emoticons. 

Multiple Choice

The bar graph shows the results of a survey at William James Middles School seventh graders.

What is the probability of choosing a career in public service?

• $\frac{1}{25}$

• $\frac{7}{25}$

• $\frac{3}{25}$

Multiple Choice

The bar graph shows the results of a survey at William James Middles School seventh graders.

Determine how many students out of 400 will enter the education field. 

• 112

• 110