BIOSTATS - lesson 2

• Methods of data collection

  1. questionnaire
  2. interview
  3. review of records
  4. observation
• Questionnaire

  • a series of questions to collect information
  • most common type to collect data
• 2 types of questionnaire

  1. open ended question
  2. closed ended question
• Open ended question

  • can elicit more detail responses
  • require more effort to encode
  • easy to administer
• Closed ended question

  • uniform or pre-coded
  • require less effort to encode
• Interview

  • Verbal communication between the researcher and the participant
• types of interview

  1. unstructured interview
  2. structured interview
• Unstructured interview

  • More conversational
  • Allows flexibility in questioning
• Structured interview

  • formal interview
  • Order of questions
• Review of Records

  • Collection of data from existing records using an abstraction form
• Observation

  • Behaviors that can be observed and measured using observation checklists or rating scales
• Data Processing

  • A systematic procedure to ensure that the information/data gathered are complete, consistent and suitable for data analysis
• Process of data processing

  • data coding
  • data encoding
  • data edting
• Data Coding

  • Transforming collected information /observation into numbers
  • number of codes must be minimum to 8
  • It should be exhaustive and mutually exclusive
• Data Encoding

  • Entering of data in a spreadsheet
  • Use computer programs for encoding
• Data Editing

  • Inspection and correction of any errors or inconsistencies
• Data Analysis

  • The process of evaluating data using analytical and statistical tools
• Considerations in choosing statistical test

  1. objective of analysis
  2. level of measurement of the variables
  3. study design
• Objective of analysis

  • Relationship tests - test for the significance of the relationship of variables
  • Difference tests - test for the significance of differences in the groups being compared
• Level of measurement of the variable

  • Parametric tests - make assumptions about the parameters of the population distribution
  • Non-parametric tests - make no assumptions about the parameters of the population distributions
• Study design

  • dictates the number of groups to be compared
  • dictates whether the samples are independent or related
• Data Presentation

  • The method of summarizing, organizing and communicating information using a variety of tools.
• Tabular Presentation - compact way of presenting data in columns and rows
• Parts of Statistical Table

  1. table number
  2. title
  3. box head or column heading
  4. stubs or row heading
  5. body
  6. foot notes
  7. source of data
• Table number

  • Refers to the relative position of the table
  • Placed on the same line as the title but separated by period
  • Use Arabic numerals
• Title

  • gives a clear and concise description of the data
  • Answer the following question: what, where, who, when
• Box Head (Column Heading)

  • Indicates the basis of classification of the columns or vertical series
• Stubs (Row Heading)

  • Indicates the basis of classification in rows or horizontal series
• Body

  • main part of the table (composed of cells)
  • contains the numerical information
• Foot Notes

  • appear immediately below the body of the table
  • provides additional information
• Source of Data

  • exact reference of the information
• Guidelines in Table Construction

  • 3 to 4 variables only per table
  • categories must be exclusive
  • All tables should have uniform style
• Dummy Table

  • skeleton tables that give a preview of what table outputs may be expected from the study
• Master Table

  • Shows the distribution of observations across several variables of interest in a study
  • Presents detailed statistical data and facilitates generation and tabulation of smaller tables
• Frequency Distribution Table

  • show either the actual number of observations falling in each range or the percentage of observations.
• Parts of Frequency Distribution Table

  1. Class interval- width of class distribution
  2. Frequency - record the number of times a result appears in class interval
  3. Cumulative frequency- add the frequency of the previous row to the frequency of the current row.
  4. Percentage-list the percentage of the frequency in each class interval
  5. Cumulative percentage- add the percentage of the previous row to the percentage of the current row.
• Types of Graphs

  • pie graph
  • bar graph
  • component bar diagram
  • histogram
  • frequency polygon
  • line graph
  • scatter plot
  • box plot
• Pie chart

  • Describe how a whole is divided into parts
  • Shows the percentage of the total number
• Bar graph

  • presents data in terms of frequencies per category
  • Used in comparing numerical measurements of qualitative variable or discrete quantitative variable
• Component Bar Diagram

  • Used for comparing the compositions of two or more different groups