Ages of US Presidents at Inauguration 57 61 57 57 58 57 61 54 68 51 49 64 50 48 65 52 56 46 54 49 51 47 55 55 54 42 51 56 55 51 54 51 60 61 43 55 56 61 52 69 64 46 54 a) Your first class interval will start with the multiple of your class size that is less than the low of your data b) Make up your classes using your class size until you get to the multiple of your class size above the high of your data (If your high is a multiple of your class size, you must go one multiple higher.) 3) Set up a frequency distribution using your chosen class interval size: Since you want between 5 and 12 classes, divide the range by 5 and 12 to determine possible class sizes (use 10 and 25 for very large sets of data) Range ÷ 12 ≤ class size ≤ Range ÷ 5 2) Find a good class interval size: 1) Find the range: High - Low= X 40-44 44-48 48-52 52-56 56-60 60-64 64-68 68-72 Total ƒ 2 3 9 11 8 5 3 2 43 6) Add the totals. Remember: Σƒ=n 5) Find the relative frequency for each class (if desired). rƒ 0.046512 0.069767 0.209302 0.255814 0.186047 0.116279 0.069767 0.046512 1.00 Don't forget to title and label your graph!! Draw in the bars neatly to size. Scale the y-axis to start at 0 and ending just above the highest frequency or relative frequency (depending on which you are making) Along the x-axis place the class boundaries to scale. 7) Take some graph paper. 4) Determine the frequency for each class. (Remember that 40 - 44 includes all numbers 40 ≤ x < 44) Example: The multiple of 4 that is less than 43 is 40 and the multiple of 4 above 69 is 72, so my classes will go 40-44, 44-48, ..., 68-72 Nice class interval sizes for this set of data would be 3, 4, or 5. For this example I chose to use 4. Example: 26 ÷ 5 = 5.2 26 ÷ 12 = 2.166667 Example: 69 - 43 = 26

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