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Methods of Presenting Data. Prepared by: Josefina V. Almeda Professor and College Secretary School of Statistics University of the Philippines, Diliman August 2009. Most of the notes are from the “Elementary Statistics” book by Almeda, Capistrano, and Sarte, 2009. 3 Ways of Presenting Data.
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Methods of Presenting Data Prepared by:Josefina V. AlmedaProfessor and College SecretarySchool of StatisticsUniversity of the Philippines, DilimanAugust 2009 Most of the notes are from the “Elementary Statistics” book by Almeda, Capistrano, and Sarte, 2009
3 Ways of Presenting Data * Textual * Tabular * Graphical
Textual Presentation * is putting important figures in the text of the report * figures may be summary statistics like the minimum, maximum, mean, median, standard deviation, percentage, or total * allows us to highlight the significant figures of the study * it confirms deductions and answers to the research problem
Example of Textual Presentation In terms of relative data availability for progress monitoring of the Millenium Develoment Goals, the Philippines ranked first in 2003 among the 11 countries in the ASEAN region. Based on the 2003 report of the United Nations Economic and Social Commission for Asia and the Pacific (UN-ESCAP), the Philippines obtained a rating of 27.9% followed by Thailand with 25.2% and Indonesia with 24.6%. The Philippines ranked fourth among all countries in the Asia and the Pacific Region, with Australia topping the list with 29.1%, followed by Japan, 29.0%, and Republic of Korea, 28.7%. According to the UNESCAP, the theoretical maximum is for a country to have 767 data values (59 series x 13 years) and a country is counted to have data available when data exist for one or more years. Source: Statistical Yearbook 2005, NSCB
Tabular Presentation * Arrangement of figures in rows and columns for easy reading and analysis * It allows us to compare and look for relationships among the variables of interest * The table can have frequency counts, proportions, percentages, and other summary measures such as totals and averages.
Formal Statistical Table * contains all the important parts of a table like table number, table title, head note, stub head, box head, column headings, footnotes, source notes, etc. * can stand alone even without an introductory statement.
Definitions of the Different Parts of a Table Headingconsists of the table number, title, and head note. It is located on top of the table of figures. Table Number identifies the position of the table in a sequence. Table Title gives the subject, classification, time, and area segments. Head note specifies the unit of measurement of the data and may provide additional explanation about the figures in the table. It is located below the table title and above the top cross rule of the table.
Box Head contains spanner heads and column headings. Spanner Head is an identifying label for the column headings. Column Heading is a descriptive label for the column cells. Panel consists of several column heads under the same spanner head.
Stub contains the stub head, center head, and row captions. Its position is at the first column of the table. Stub head is a descriptive label for the center heads and row captions. Center head is an identifying label for the row captions. Row caption is a descriptive label for the row cells. Block contains row captions under the same center head.
Field is set of numerical figures in the table. Line is a row of cell figures. Column is a column of cell figures. Cell is the numerical figure in the intersection of a row caption and column heading. Footnote is an explanatory text about a specific part or the whole table. Its position is at the bottom of the table. Source note gives the name of the agency that collected the data. Its position is at the bottom of the table.
The Parts of a Formal Statistical Table panel TABLE NO. - Title of the Table (head note) Line b l o c k k field *Footnote Source note:
Table Titles • The Title is descriptive of the table • It answer four (4) questions about the subject matter of its table: • WHAT? • HOW CLASSIFIED? • WHERE? • WHEN?
Table 1. Amount of Pag-ibig Provident Benefits Refunded and Number of Claimants By Regional Group; January to May 2002 Universe Segment Classification and Area Segment Time Reference Segment
TABLE 2. Total Number of Families, Total and Average Annual Family Income and Expenditure by Income Class, Urban and Rural in the Philippines: 2000 (in thousand pesos) head note heading Spanner head Example of a formal statistical table row captions Note: Totals may not add up due to rounding footnote Source: NSO source note
Graphical Presentation * It is a good means of communicating the numerical figures found in tables * Charts facilitate analysis when it reveals probable relationships among variables * It allows comparison of different series or groups * Placing figures in charts permits us to validate conclusions made in the study.
Notes: * Charts show only approximations and the general picture of the data set. * A good chart must be accurate, clear, simple, professional looking, and has a well-designed layout. * The arithmetic scale should have equal increments to represent equal numerical units. * The chart should have no visual illusions with the incorrect use of shadings or patterns. * We should put chart titles, scale figures and labels, and legends, if necessary.
Types of statistical charts * line chart * vertical bar chart * horizontal bar chart * pictograph * pie chart * statistical map
Definitions of Parts of a Chart Chart Title * gives the subject, data classification, time reference, and area segment of the data set * located above or below the chart Coordinate Axes * are the horizontal and vertical axes * spacing of the units may be different for the horizontal and vertical axes but must remain constant within the same axes. Point of Origin * is the intersection of the horizontal and vertical axes.
Scale Divisions * are the ticks to denote the scale pointsof the horizontal and vertical axes Grid Lines or Coordinate Lines * may be horizontal or vertical * guides the reader in reading the numerical figures * must be lighter than the curves on the chart to maintain the focus on the chart * choice of horizontal or vertical grid line depends upon the type of chart.
Scale Figures * run from left to right for the horizontal axis and from bottom to top for the vertical axis * use multiples of five or other easy to work with multiples for scale values * for big scale values, limit the number of digits of the scale figures to one or two, then; place the unit of measurement in the scale legend * position the scale figures near the coordinate axes * scale figure of the vertical axis starts with zero (for line chart and vertical bar charts) * if we only need the upper part of the coordinate fields to portray the data, we still retain the zero but exclude the lower part of the figures by putting a break on the vertical scale
Example of Putting a Break on the Vertical Axis Figure 1a Figure 1b 8080 6060 40 40 0 0 Time Period Time Period
Scale Labels or Scale Legends * describes both horizontal and vertical axes Curves * represent the plot of the data series * differentiate several curves by using different patterns or colors. Curve Legends * give the type of data series * legend symbol follows the color or patterns selected for a particular curve * we prefer the use of curve labels than curve legends.
Footnote * brief explanation to any part of the chart * located at the bottom of the chart Source Note * indicates the source of the data * located at the bottom of the chart
Line Chart * appropriate for time series data * emphasis is on the movement * shows trends, patterns, forecasts * applicable for one or more time series data for comparison purposes
Notes for Line Chart: • * put the variable of interest on the vertical axis and the time on • the horizontal axis • * put appropriate scale legends for both axes • * position the scale figures on the tick marks • * ratio of height of width should be 2 to 3 or 3 to 4
Figure 2. Different Parts of a Line Chart Figure 2. Number of Reported Cases and Deaths Due to Dengue Fever in the Philippines: 1992 to 2000 50 45 40 35 30 25 in thousands 20 15 10 5 0 92 93 94 95 96 97 98 99 2000 Figure title Curve label Grid lines Reported cases Border Death cases Scale figures Source Note Source: Department of Health
FIGURE 3a. Stretched Out Vertical Axis of the Grid 20 15 Sales in Millions 10 FIGURE 3b. Stretched Out Horizontal Axis of the Grid 20 5 15 Sales in Millions 10 5 0 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 TIME TIME FIGURE 3. Stretched Out Vertical and Horizontal Axes and Its Consequences
FIGURE 4. Line Chart with Two Curves and Large Observed Values
Figure 5a. Simple Line Chart • has only one curve • appropriate for one series of time • data. • Figure5b. Multiple Line Chart • shows two or more curves • to compare the trends in two or • more data series Court of Appeals Supreme Court FIGURE 5. Types of Line Chart
Column Charts * for showing comparisons of amount of a variable of interest collected over time * emphasis is on the magnitude of the data set
Figure title border Horizontal grid lines Scale label Source note Source: NSO FIGURE 6. Different Parts of a Column Chart * The height of the column represents the amount of a specific time. * Columns must not be too long or too short, not too wide or too narrow. * The space between the bars must not be too wide or narrow. * The usual space between bars is around one-fourth of the width of the column.
FIGURE 7. Illustrations of Incorrect Width and Spacing of Columns
Notes on Column Charts: * vertical scale of the column chart should start with zero * do not put a break on the vertical scale * use scale figures that are multiples of 5, 10,…,50 * if the observed values are small, use multiples of 2 * put a scale label to identify the variable of interest * put horizontal grid lines * for one series of data, use only one color or pattern * for two or more series of data, use different colors, shadings or patterns * avoid wavy or unconventional patterns
Types of Column Charts * Simple Column Chart * Grouped Column Chart * Subdivided Column Chart * 100% Subdivided Column Chart * Net Deviation Column Chart
FIGURE 9a. Simple Column Chart FIGURE 9b. Grouped Column Chart • for one time series data • emphasizes on the amount of • increase or decrease • columns must have only one • pattern, color, or shading • for comparing two or more time • series data by using different • colors, shading, or patterns
FIGURE 9c. Subdivided Column Chart FIGURE 9d. 100% Subdivided Column Chart • components are in percentages • facilitates comparison of two or • more series • Use different shades, patterns, • or colors to show the component • parts in percentages • to show the component parts of • a series of values • Use different shades, patterns • or colors show the different • components of the column.
FIGURE 9e. Net Deviation Column Chart • for showing increases and • decreases, gains and losses, and • positive and negative numbers • over time. • vertical axis will have positive • and negative scales
Horizontal Bar Charts * for qualitative types of data given a specific time * to compare the magnitudes of the different categories of a qualitative variable * place the categories of the qualitative variable on the y-axis and the amount or number is on the horizontal axis * use vertical grid lines
Figure title Scale label Border Vertical grid lines Scale figure Source note Source: DOH FIGURE 10. Different Parts of a Simple Horizontal Bar Chart
Notes on Horizontal Bar Chart: * the length of the bar represents the value for the category * the bars should not be too wide or narrow or too long or too short * the spaces in between the bars may be one-fifth to one-half the width of the bar * arranging the bars according to length facilitates comparisons * use appropriate colors or patterns for the bars * place the title of the chart at the center of either the top or bottom of the chart
Types of Horizontal Bar Charts * Simple Bar Chart * Grouped Bar Chart * Subdivided Bar Chart * Subdivided 100% Bar Chart
FIGURE 11a. Simple Bar Chart FIGURE 11b. Grouped Bar Chart • compares the amounts of two • or more data sets with the • same set of categories • number of bars per category • depends upon the number of • groups in the data set • for showing the magnitude of • the different categories of a • qualitative type of variable • length of the bar represents the • value of each category
FIGURE 11c. Subdivided Bar Chart FIGURE 11d. Subdivided 100% Bar Chart • for various categories, we • divide one bar into several • components • uses absolute numbers in the • scale values • It indicates the parts of a whole • such that the parts total to 100%.
Pie Chart * circle divided into several sections * each section indicates the proportion of each component or category * useful for data sorted into categories for a specific period * purpose is to show the components parts with respect to the total in terms of the percentage distribution * use the pie chart if there are less than 6 categories in the data set
Notes on Pie Chart: * arrange components of the pie chart according to magnitude * If there is an “Others” category, we put it in the last section * Use different colors, shadings, or patterns to distinguish one section of the pie to the other sections * Plot the biggest slice at 12 o clock
Pictograph * gives an approximation only of the actual figures * compares the different categories * symbols selected should be self-explanatory and easy to understand * each symbol represents a number
Figure 13. Illustration of a Pictograph Population in the Philippines for Census Years 1980 to 2000 Source: NSO