Frequency Distributions Step 1: Find Classes

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Frequency DistributionsStep 1 Find Classes

• Find Class Width
• Range of Classes Desired
• Find Lower Class Limits
• Lowest Class Width 1st of next Class
• Continue to get of classes desired
• Find Upper Class Limits
• Add (CW-1) to lower limits
• Check to make sure limits include all data

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Lower Class Limits

• Range/classes CW
• (65-24)/6 6.8 7 CW
• 24 (7)
• 31 (7)
• 38 (7)
• 45 (7)
• 52 (7)
• 59

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Upper Class Limits

• Start Lower Class Limit (CW-1)
• 24 (6) 30
• 31 (6) 37
• 38 (6) 44
• 45 (6) 51
• 52 (6) 58
• 59 (6) 65

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CLimits 24 - 30 31 37 38
44 45 51 52 58 59 65
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Step 2 Find Class Boundaries Used for neater
graphs

• Subtract .5 from all Lower Class Limits
• 24 - .5 23.5
• 31 - .5 30.5 cont. .
• Then Add .5 to all Upper Class Limits
• 30 .5 30.5
• 37 .5 37.5 cont. .

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Class Limits and Boundaries

• CLimits CBoundaries
• 24 - 30 23.5 30.5
• 31 37 30.5 37.5
• 38 44 37.5 44.5
• 45 51 44.5 51.5
• 52 58 51.5 58.5
• 59 65 58.5 65.5

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Step 3 Tally and Freq Columns

• Tally Column is the location for your tick marks
• Frequency Column lists the of tick marks
• Relative Freq Column may be added
• Freq/N x 100relative freq (as s)
• Cumulative Freq Column may be added
• Sum of freqs in lines above

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CLimits CBoundaries Tally Freq
RelFreq CumFreq 24 - 30 23.5
30.5 31 37 30.5 37.5 38 44 37.5
44.5 45 51 44.5 51.5 52 58
51.5 58.5 59 65 58.5 65.5
/// 3 3/2512 3 / 1 1/254 4 /////
5 5/2520 9 ///// //// 9 9/2536 18 /////
/ 6 6/2524 24 / 1 1/254 25
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Frequency
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Relative Freq
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OGIVE Cum Freq