Chapter 9 Quiz
Study Guide
Topics on Quiz:
Scheduled for Thursday, May 7th 2015
-Scatter Plots (Lesson 1 pgs 665-674)
-Lines of Best Fit (Lesson 2 pgs 677684)
-Two-Way Tables (Lesson 3 pgs 689696)
Scatter Plots:
Types of Associations:
-Five-Number Summary/Box and
whisker plot (Lesson 4)
-Analyze Data Distributions (Lesson 6
pgs 717-724)
Constructing a Scatter Plot:
Example:
BOATING Rehan’s
yacht holds 70 passengers. Each hour he stops at the marina to let some
passengers off and on. The table shows how many passengers are on board during each hour
of boating.
Hour
Passengers
1
30
2
40
3
32
4
40
5
55
a. Construct a scatter plot of the data. Then draw and assess a line that seems to best represent
the data.
Steps:
1. Identify your x and y’s
2. Graph all points  (1,30) (2,40) (3,32) (4,40) (5,55)
This shows a positive association.
Lines of Best Fit:
A line of best fit is a line that is very close to most of the data points (should be
even amount of points above and below the line)
Ex: Using graph above find the line of best fit:
This line has about 2 points above and below the line
Step 2: Choose any two points on the line (don’t have to be data points): Ex:
(1,30) and (5,50)
Step 3: Use these points to find the slope of the line
(1,30) and (5,50)
x1,y1
x2,y2
m=
𝑦2−𝑦1
𝑥2−𝑥1
-- m =
50−30
5−1
=
20
4
=5
Step 4: Use point-slope form  y – y1 = m(x – x1)
y – 30 = 5 (x – 1)
Distribute: y – 30 = 5x -5
Solve for y: y = 5x + 25
 equation for line of best fit
Example: Use the line of best fit from the example above (y = 5x + 25) to make a
conjecture about the number of passengers on the boat during hour 7.
Answer: Look at the line to estimate the number of passengers on the boat during
hour 7. There is a point at (7,60). So there are 60 passengers on the boat at hour 7.
Or
Substitute 7 in for x into the equation
Y= 5x + 25
Y=5(7) + 25
Y= 35+ 25
Y= 60
Answer: 60 passengers
Two-Way Tables:
There are 195 male and 126 female students at McGuffey Junior High. A survey showed that
110 males and 84 females ride the bus.
a. Complete the table to show the data
Steps: Fill in the information you know. There are a total of 195 males and 126
females:
Bus
Not Bus
Total
Males
195
Females
126
Total
-110 males and 84 females ride the bus:
Bus
Not Bus
Total
Males
110
195
Females
84
126
Total
Given this information you can complete the table:
Bus
Not Bus
Total
Males
110
85
195
Females
84
42
126
Total
194
127
321
b. What is the relative frequency of males who ride the bus?
Steps: Divide the number of males who ride the bus (110) by the total number of males (195)
110
195
= 56.4%
c. What is the relative frequency of females who ride the bus?
84
126
= 66.7%
Lesson 4: Descriptive Statistics
Mean (average), Median, Mode and Range:
Box and Whisker Plot:
Example:
Draw a box plot of the data:
80
92
Test Scores
88
81
88
87
79
Step 1: Find the median
Median Arrange the values from least to greatest and find the middle value.
79, 80, 81, 87, 88, 88, 92
Q2
Step 2: Find the first quartile (Q1) and third quartile (Q3): Q1 = 80 and Q3 =88
79, 80, 81, 87, 88, 88, 92
Q1
Q2
Q3
Step 3: Find the minimum and maximum value: (minimum= 79, maximum= 92)
79, 80, 81, 87, 88, 88, 92
Q1
Q2
Q3
Step 4: Drawing the box plot
-Draw a number line that includes the least and greatest numbers in the data.
-Mark the minimum and maximum values, the median, and the first and third quartiles above the
number line.
-Draw the box plot and assign a title to the graph.
What conclusion can be made from the graph? (Remember that are 4 quarters  25% each)
Possible Conclusions:
-50% of the grades are below 87
-50% of the grades are above 87
-First quarter scores are very close together
-2nd quarter scores are spread out
Analyze Data Distribution:
Example: