Lesson 14-1

Example 1
ELECTRONICS  The following data relates the age of a student with average amount of time (in hours) daily spent using electronics for the years 1990 and 2003.

	Hours Spent Using Electronics	
	Grade School	Middle School	High School	College	
1990	5	12	15	11	
2003	18	23	27	25	

a.	Make a back-to-back bar graph that represents the data.

b.	Describe any trends indicated by the graph.

a.	Let the age of the student be the central axis. Draw a horizontal axis that is scaled 0 to 30 in each direction. Let the left side of the graph represent 1990 and the right side of the graph represent 2003. Draw the bars to the appropriate length for the data.		

b.	You can see from the graph that when you compare each age group of students, the amount of electronic usage increases from grade school through high school and then slightly decreases in college. The usage increased dramatically from 1990 to 2003 in all groups.

Example 2
DRIVING  The speeds of cars traveling on a particular stretch of highway are shown below.

	69    72    65    61    75    81    72    64    59    83
	77    68    70    73    80    66    69    74    67    65

a.	Find the range of the data

b.	Determine an appropriate class interval.

c.	Find the class marks.

d.	Construct a frequency distribution of the data.

e.	Draw a histogram of the data.

f.	What conclusions can you determine from the graph?

a.	The range is 83 – 59 or 24.

b.	An appropriate class interval is 10 miles per hour, beginning with 50 miles per hour and ending with 89 miles per hour. There will be four classes.

c.	The class marks are the averages of the class limits of each interval. The class marks are 55, 65, 75, and 85.

d.	Make a table listing class limits. Determine the number of recorded speeds in each interval.

Speed	Frequency	
50-60	1	
60-70	9	
70-80	7	
80-90	3	

e.	Label the horizontal axis with the class limits. The vertical axis should be labeled from 0 to a value that will allow for the greatest frequency, 9. Draw the bars side by side so that the height of each bar corresponds to its interval’s frequency.

	You can also use a graphing calculator to create the histogram. In statistics mode, enter the class marks in the L1 list and the frequency in the L2 list. Set the window using the class interval for Xscl, and select the histogram as the type of graph.		

f.	The majority of the speeds tended to be between 60 and 80 miles per hour.

Example 3
HEALTH  A medical researcher collects the current weights of 20 people who are applying to participate in a new diet program. The data is shown below.

	162    176    214    141    195    223    184    179    188    255
	132    157    203    185    166    148    224    228    194    172

a.	Find an appropriate class interval. Then name the class limits and the class marks.

b.	Construct a frequency distribution.

c.	Use a graphing calculator to draw a frequency polygon.

a.	The range of the data is 255 – 132 or 123. An appropriate class interval is 25 pounds. The class limits are 125, 150, 175, 200, 225, 250, and 275. The class marks are 137.5, 162.5, 187.5, 212.5, 237.5, and 262.5.

b.	Weight	Frequency	
	125-150	3	
	150-175	4	
	175-200	7	
	200-225	4	
	225-250	1	
	250-275	1	

c.	In statistics mode, enter the class marks in the L1 list and the frequencies in the L2 list. Set the window using the class interval for Xscl, and select the line graph as the type of graph.