LESSON 7-1 Frequency Tables, Stem-and-Leaf Plots, and Line Plots Lesson Objectives Organize and interpret data in frequency tables, stem-and-leaf plots, and line plots Vocabulary frequency table (p. 80) cumulative frequency (p. 80) stem-and-leaf plot (p. 81) line plot (p. 81) Additional Eamples Eample 1 The list shows the average high temperatures for 20 cities on one February day. Make a cumulative frequency table of the data. How many cities had average high temperatures below 9 degrees? 9,,, 1, 0, 0,, 1, 8, 2, 2, 28, 20, 18, 12, 8, 8,, 2, 2 Step 1: Look at the to choose equal intervals for the data. Step 2: Find the number of data values in each interval. Write these numbers in the column. Step : Find the for each row by all the frequency values that are above or in that row. February Temperatures in 20 Cities Average Highs Frequency Cumulative Frequency cities had average high temperatures below 9 degrees. 171 Holt McDougal Mathematics
Eample 2 The data shows the number of years coached by the top 1 leaders in alltime NFL coaching victories. Make a stem-and-leaf plot of the data. Then find the number of coaches who coached fewer than 2 years., 0, 29,, 21, 2, 2, 22, 19, 21, 18, 2, 1, 1, 1 Step 1: Find the least data value and the greatest data value. Since the data values range from to, use tens digits for the and ones digits for the. Step 2: List the Step : List the from least to greatest on the plot. for each stem from least to greatest. Step : Add a and a. The stems are the digits. The leaves are the digits. coaches coached fewer than 2 years. 172 Holt McDougal Mathematics
Eample Make a line plot of the data. How many hours per day did Morgan babysit most often? M T W Th F S Su Wk 1 0 8 2 Wk 2 2 7 7 7 0 8 Wk 0 8 1 2 Wk 8 0 Step 1. The data values range from to. Draw a number line that includes this range. Step 2. Put an X above the number on the number line that corresponds to the number of miles Morgan each day. The greatest number of X s appear above the number. This means that Morgan babysat for hours most often. Check It Out! 1. The list shows the grades received on an English eam. Make a cumulative frequency table of the data. How many students received a grade of 79 or below? 8, 8, 77,, 99, 90, 80, 8, 9, 72, 0,, 9, 8, 79, 87, 8, 9, 71, 9 English Eam Grades Grades Frequency Cumulative Frequency 17 Holt McDougal Mathematics
LESSON 7-1 Frequency Tables, Stem-and-Leaf Plots, and Line Plots Lesson Objectives Organize and interpret data in frequency tables, stem-and-leaf plots, and line plots Vocabulary frequency table (p. 80) A table that organizes data into categories or groups. cumulative frequency (p. 80) A running total of the number of data items. stem-and-leaf plot (p. 81) A graph that uses digits to organize and display a set of data. line plot (p. 81) A graph that shows how many times each data value occurs. Additional Eamples Eample 1 The list shows the average high temperatures for 20 cities on one February day. Make a cumulative frequency table of the data. How many cities had average high temperatures below 9 degrees? 9,,, 1, 0, 0,, 1, 8, 2, 2, 28, 20, 18, 12, 8, 8,, 2, 2 Step 1: Look at the range to choose equal intervals for the data. Step 2: Find the number of data values in each interval. Write these numbers in the Frequency column. Step : Find the cumulative frequency for each row by adding all the frequency values that are above or in that row. February Temperatures in 20 Cities Average Highs Frequency Cumulative Frequency 0 19 20 9 0 9 0 79 7 7 12 17 20 17 cities had average high temperatures below 9 degrees. 171 Holt McDougal Mathematics
Eample 2 The data shows the number of years coached by the top 1 leaders in alltime NFL coaching victories. Make a stem-and-leaf plot of the data. Then find the number of coaches who coached fewer than 2 years., 0, 29,, 21, 2, 2, 22, 19, 21, 18, 2, 1, 1, 1 Step 1: Find the least data value and the greatest data value. Since the data values range from 1 to 0, use tens digits for the stems and ones digits for the leaves. Step 2: List the Step : List the stems leaves from least to greatest on the plot. for each stem from least to greatest. Step : Add a key and a title. The stems are the tens digits. The leaves are the ones digits. Number of Years Coached Stems Leaves 1 2 1 0 1 8 9 2 9 Key: 2 1 means 21 11 coaches coached fewer than 2 years. 172 Holt McDougal Mathematics
Eample Make a line plot of the data. How many hours per day did Morgan babysit most often? M T W Th F S Su Wk 1 0 8 2 Wk 2 2 7 7 7 0 8 Wk 0 8 1 2 Wk 8 0 Step 1. The data values range from 0 to 8. Draw a number line that includes this range. Step 2. Put an X above the number on the number line that corresponds to the number of miles Morgan 0 1 2 7 8 babysat each day. The greatest number of X s appear above the number. This means that Morgan babysat for hours most often. Check It Out! 1. The list shows the grades received on an English eam. Make a cumulative frequency table of the data. How many students received a grade of 79 or below? 8 8, 8, 77,, 99, 90, 80, 8, 9, 72, 0,, 9, 8, 79, 87, 8, 9, 71, 9 English Eam Grades Grades Frequency Cumulative Frequency 0 9 70 79 80 89 90 99 8 1 20 17 Holt McDougal Mathematics