Frequency Tables and Dot Plots Lesson Objective Common Core Standard To analyze a set of data by finding the range and by making frequency tables and dot plots Statistics and Probability Vocabulary A frequency table is a table that lists each item in a data set with the number of times the item occurs. A dot plot a graph that shows the shape of the data by stacking dots above each data value on a number line. difference between the least and greatest values. The range of a data set is the Example 1 Frequency Table The favorite lunch choices of ten students are: pizza, pizza, chicken, hamburger, chicken, pizza, chicken, pizza, pizza, pizza. Organize the data in a frequency table. Find the mode. Favorite Lunch Lunch Tally Freq. hamburger 1 pizza 6 chicken 3 The number of tally marks in each row is the pizza Since the most students selected pizza lunch item, the mode is Make a tally mark for each lunch item chosen. frequency . as their favorite . Quick Check 1. The first initials of the names of 15 students are listed below. A J B K L C K D L S T D V P L Organize the data in a frequency table. Find the mode. Initial A B C D J K L P S T V 1 1 1 2 1 2 3 1 1 1 1 Tally Frequency The mode is L . 441196_C1_Ch9_WKbk_Ver-1.indd 102 03/10/12 5:08 PM Examples 2 Using a Dot Plot Make a dot plot to display the dinner hour for seven families: 7:00 5:00 6:00 6:00 8:00 7:00 6:00 Dinner Hours • • • • • • • 5 6 7 8 d Each • represents one family. d The scale of a graph includes all of the data values. The scale is 5 to 8 in this line plot. 3 F inding the Range Find the range of the data in Example 2. ← Subtract the least from the greatest value. 8 255 3 The range of dinner times is 3 hours. Quick Check 2. Use a dot plot to interpret the number of sales calls made each hour: 2, 3, 0, 7, 1, 1, 9, 8, 2, 8, 1, 2, 8, 7, 1, 8, 6, 1. Number of Phone Calls 0 1 2 3 4 5 6 Phone Calls 7 8 9 3. T he numbers of pottery items made by students are 36, 21, 9, 34, 36, 10, 4, 35, 30, 7, 5, and 10. Find the range of the data. 32 441196_C1_Ch9_WKbk_Ver-1.indd 103 03/10/12 5:08 PM

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