Lesson Summary Students weigh the 14 objects from Lesson 3 using a spring scale. They will compare the weights to their predictions. Students create a graph comparing size and weight of the objects.  As a class, students discuss their results and share opinions about accuracy. Teacher Background During this lesson, mode, median, and mean are introduced. The students will choose what is most appropriate to express the average of their results. The median or mode is the more suitable average for this investigation.  As a class, it is necessary to discuss the level of precision that students can expect with the spring scale. Set-up/Management Tips A blank bulletin board, chalkboard, or wall space is needed for the class graph. This class graph will be referred to in future lessons.  When weighing objects from the bag, children often have trouble attaching the object to the bobby pin clip. It may require multiple attempts.  To remedy this problem, children often want to add masking tape to the object. Discuss why this may not be the best strategy. After this investigation, make sure the objects are counted. Literacy Support Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: Mode Median Mean   Average   Design