DATA ORGANIZATION AND PRESENTATION Flashcards
Give examples of forms into which data can be arranged
- Arrays
- Frequency tables
- Stem and leaf plot
- Tabulations: Simple tables and cross tabulation
What are the different types of arrays and their limitations
1.Simple arrays
A simple array is an arrangement of data in an ascending or descending order. It’s convenient if the number of it’s small. As the number of items increases, the series become too long and unmanageable. Thus there is need to condense the data.
- Frequency array
It’s a series formed on the basis of frequency with which each item is repeated in a series.
Its main limitation is that it does not give the idea of the characteristics of groups. For example, it does not tell us how many students have obtained marks between 45 -50. It’s not possible to compare characteristics of different groups. This limitation is removed by frequency distribution tables
Describe the frequency distribution and give its limitation
A frequency distribution table lists categories of scores/items along with their corresponding frequencies. The downside of frequency distribution tables is that, while the frequency of each class is easy to see, the original data points have been lost. This can be solved by using Stem and leaf plot
What are class boundaries and how are they computed
The class boundaries are used to separate the classes so that there are no gaps in the frequency distribution. They are obtained by increasing the upper class limits and decreasing the lower class limits by the same amount so that there are no gaps between consecutive under classes. The amount to be added or subtracted is 1⁄2 the difference between the upper limit of one class and the lower limit of the following class. The rule of thumb is that the class limits should have the same decimal place value as the data, but the class boundaries should have one additional place value.
What are the guidelines for constructing a frequency distribution table
- The classes must be mutually exclusive. That is, each score must belong to exactly one class.
- The classes must be exhaustive meaning there should be enough classes to accommodate all data. Include all classes, even if the frequency might be zero.
- All classes should have the same width, to avoid a distorted view of data. One exception occurs when a distribution has a class that is open – ended such as “65 years or older”.
- The number of classes should be between 5 and 20.
Describe a stem and leaf plot
A stem and leaf plot shows us potential
patterns in the responses that may not be apparent in the
original listing of the data
What are the steps for constructing a stem and leaf plot
Step 1: Find the least number and the greatest number in the data set
Step 2: Draw a vertical line and write the digits in the tens places from 1 to 3 on the left of the line. The tens digit form the stems.
Step 3: Write the units digit to the right of the line. The units digits form the leaves.
Step 4: Rewrite the units digits in each row from the least to the greatest.
Step 5: Include an explanation.
*See notes for examples
What is a table
A table is a systematic arrangement of statistical data in columns and rows
Rows are horizontal arrangements while columns are vertical arrangements
The purpose of a table is to simplify the presentation and to facilitate comparison.
What are the 8 essential parts of a table
(i) Table Number: For distinguishing one tables. (ii) Title of the Table: be short & clear. Shows know the nature of the data contained in the table. It is either placed just below the table number or at its right. (iii) Caption: headings of the columns. Column heading is written in the middle of a column in small letters. (iv) Stub: headings of rows. (v) Body It contains a number of cells. Data are entered in these cells.
(vi) Head Note/ prefatory note:
contains the unit of measurement of data. It is usually placed just
below the title or at the right hand top corner of the table.
(vii) Foot Note
It helps in clarifying the point which is not clear in the table. A foot note may be keyed to the title or to any column or to any row heading. It is identified by symbols such as *,+,@,£ etc.
*See notes for examples
Describe simple tables and cross tabulation
1.Simple (One-Way) Tables
Here, only one characteristic is shown.
2.Cross Tabulation
Here, more than one characteristic is included in a table. They are a good way to compare two subgroups of information. Cross tabs allow you to compare data from two questions to determine if there is a relationship between them.
*See notes for examples
What are the ways in which data is presented
Pictograms and graphs
What are pictograms?
Data is represented using a self-explanatory pictorial symbol. They are attractive and easy to remember but are limited when dealing with large quantities.
Give 7 examples of graphs in research
- Bar graphs
- Histograms
- Line graphs
- Pie charts
- Pictograms
- Frequency polygons
- Cumulative frequency curve (ogive)
Describe and give examples of the 5 types of bar graphs
• Simple bar graphs
Used to represent only one variable. Only the length of the bars varies and they are very easy to read. The limitation is that they can only present one classification or category of data.
• Subdivided bar graphs
The bars are divided into more than one component. They require an index or a key to distinguish the different components. They are useful in presenting a set of distribution ratios diagrammatically.
• Multiple bar graphs
graphs: used to represent two or more interrelated data sets. Different shades or patterns can be used to distinguish between the bars. They are useful when making a comparison between two or more related variables.
• Percentage bar graphs
bars: Useful in statistical work which requires portrayal of relative changes in data. The length of the bars is kept equal to 100 and segments are cut in the bars to represent the components (percentages ) of an aggregate.
• Deviation bars
Used to represent net quantities such as net profit, net loss etc. The bars can have both negative and positive values. The positive values are shown above the base line and the negative values below it.
*See notes for pictures
Describe a pie chart
Used to show proportions of different categories of classes. They are less effective than bar graphs when the categories are many. Not advisable to use if there are more than five or six categories.
