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2.1 Frequency Distributions.notebook
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Frequency Distribution:
A. Categorical Frequency Distribution (ex: pg. 39):
STEPS:1. Make a table including: __________, __________, ______________,
_____________ (Optional)2. Tally the data and place the results in the Tally column.3. Count the tallies and place the result in the Frequency column.4. Find the percentage of values in each class:
5. Find the totals for the Frequency and Percent columns.
2.1: frequency dıstrıbutıons
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B. Grouped Frequency Distribution (ex: pg. 39):
Class Limits Class Boundaries Tally Frequency
10 – 14 9.5 – 14.5 ||| 3
15 – 19
20 – 24
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Class Boundaries:
*Rule of Thumb with Rounding: Class limits should have the _______ decimal place value as the data, but the class boundaries should have _____ __________________ place value and end in a 5.
Ex:
Class Limits Class Boundaries
7.8 – 8.8
8.9 – 9.9
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Class Width:
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Rules for Constructing a Frequency Distribution:
1. _____________________________________________________________________
*It is important to have enough classes to present a clear description of the collected data.
2. _____________________________________________________________________
*This ensures that the midpoint of each class has the same place value as the data.
Class Midpoint:
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3. _____________________________________________________________________
*Nonoverlapping class limits so that the data cannot be placed into two classes.
Ex: Age Age
10 – 20
20 – 30
30 – 40
40 – 50
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4. ___________________________________________________________________
*Even if there are no values in a class, the class must be included in the frequency dist.
*Exception: When the class with a zero freq is the first or last class, these can be omitted.
5. ___________________________________________________________________
*There should be enough classes to accommodate all the data.
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6. _____________________________________________________________________
*Avoid distorted views of the data.*Exception: When a distribution has a class that is openended (no specific beginning or ending value). This is called an openended distribution.
Ex:
Age Frequency Minutes Frequency
10 – 20 5 Below 110 16
21 – 31 10 110 – 114 25
32 and above 8 115 – 119 38
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STEPS:1. Determine the # of classes
2. Find the highest value and the lowest value
3. Find the range: R = _____________________________________________
4. Select the number of classes desired (between 5 and 20)
5. Find the class width:
6. Round the width up to the nearest whole number. If there is no remainder, add an extra class to accommodate all of the data.
7. Select a starting point for the lowest class limit. This can be the smallest data value or any convenient number less than the smallest data value.
8. Add the width to the lowest class limit to get the lower limit of the next class. Keep adding until you have the number of desired class (chosen in Step 1).
9. Subtract one unit from the lower limit of the second class to get the upper limit of the first class. Then add the width to each upper limit to get all of the upper limits.
10. Find the class boundaries.
11. Tally the data and find the numerical frequencies from the tallies.
12. Percentage column is only necessary when specifically asked for.
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C. Cumulative Frequency Distribution (ex: pg. 43):
*This gives an ascending cumulative frequency.
Ex:
Cumulative Frequency
Less than 9.5 0
Less than 14.5 3
Less than 19.5
Less than 24.5
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D. Ungrouped Frequency Distribution (ex: pg. 44):
Ex:
Class Limits Class Boundaries Tally Frequency
12 11.5 – 12.5 || 2
13
14
15
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Reasons for Constructing Frequency Distributions:
1. To _____________________ the data in a meaningful, intelligible way
2. To enable the reader to determine the __________ or _________ of the distribution
3. To facilitate computational procedures for measures of _________________ and spread (Chapter 3)
4. To enable the researcher to draw ________ and __________ for the presentation of data
5. To enable the reader to make ____________________ among different data sets.
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Homeworkpg. 46 #1 10
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