Math Background

Graphing Data
When Students Ask

  • When should I use a tally chart?
    Children may have used tally charts to keep track of points in a game. Explain that they can also use a tally chart to collect data. Let's say they want to know the favorite fruit of their classmates. If they make a tally chart with different categories of fruit, it can help them keep the data organized, making it easy to read and understand. Since the tallies are organized into groups of five or less, they are easy to count. Once children have gathered information, they can take the tallies and represent them in a bar graph.
  • Are tally charts and tables the same?
    Tally charts and tables are two ways to show data. In a tally chart, tallies are used to show the number in each category. In a table, the numbers themselves are used. Tally charts are good for collecting data because you can keep counting tallies as needed. With a table you need to keep changing the number as you collect your information.
  • Why are graphs useful?
    Lead children to see that putting data into graphs helps them organize and visualize the data, making it easier to compare and making it easier to solve problems. Show children a box containing several crayons of different colors. Ask them for which color are there the most crayons. Then show them a bar graph or pictographs representing the number of crayons for each color. By looking at a bar graph or a pictograph, they can quickly and easily see which color has the most or least crayons. Lead them to see that a graph allows them to find information fast.
  • How do I know what each picture stands for on a pictograph?
    Explain that whenever they read a pictograph, children should start by looking at the key. This tells what each picture represents. If the key indicates that each picture stands for two, then they need to count the pictures by twos to find the total number of items. If the key indicates that each picture stands for five, then they need to count the pictures by fives. If there is no key, or if the key says that each picture stands for one, just count the number of pictures by ones.
  • How are bar graphs different from pictographs?
    Pictographs use pictures to represent information. Bar graphs use bars or colored blocks on a grid and numbers to show data. In order to read a pictograph, you count the number of pictures; to read a bar graph, you simply read the number where the bar ends for each category.
  • Why do I need to learn about range and mode?
    Explain that range and mode help them to compare data. Range tells how varied the data are. If the range is a lesser number, then all the data are very close. If the range is a greater number, then the data are very different. Lead children to see that if they were to compare the heights of second-graders, the range of data would be much less than if they were to compare the heights of all the people in a family. Mode shows which category is the most common or popular. If children wanted to know the favorite animal, color, or food of a group of people, the mode of the data would be the answer given most often.

Houghton Mifflin Math Grade 2