Data Processing in Biostatistics and Epidemiology

Primary Data

Data collected by the investigator himself.

Secondary Data

Data that the investigator makes use of from other agencies.

Data Collection

Primarily done through observation and/or measurement of an empirical event, which may be perceived by the senses.

Suitability

If these data are collected accurately and systematically, their suitability will be very positive.

Methods of Data Collection

Includes various techniques such as direct personal interviews, indirect oral interviews, and mailed questionnaire method.

Primary Data Collection

These data involve large expenses in terms of money, time, and manpower.

Secondary Data Collection

These should be used with great care and caution.

Population

The entire group that you want to draw conclusions about.

Sample

The specific group that you will collect data from; should be representative of the population.

Parameter

A number that describes something about the whole population.

Data Coding

Conversion of verbal/written information into numbers which can be more easily encoded, counted, and tabulated.

Constant

Value of a characteristic that remains the same from person to person, from time to time, or from place to place.

Variable

Characteristics of different values.

Codes

Actual numerical character symbols of verbal responses.

Data Processing

A systematic procedure to ensure that the information/data gathered are complete, consistent, and suitable for analysis.

Field Code

Actual value or information given by the respondent.

Bracket Code

Recorded as a range of values rather than actual values.

Factual Code or Listing Code

Codes are assigned to a list of categories of a given variable.

Coding Manual

A document which contains a record of all codes assigned to the responses to all questions in the data collection forms.

Pattern Code or Variable Code

Applicable for questions with multiple responses.

Data Encoding

Entering the data/responses in a spreadsheet.

Data Editing

Inspection and correction of any errors or inconsistencies in the information collected.

Field Editing

Reviewing the accomplished data collection forms while still on field/area where data are to be collected.

Central Editing

Checking of inconsistencies and incorrect entries after receiving the questionnaire from the field.

1. Spot Checking

2. Eyeballing

3. Logic Check

Three Methods of Cleaning Data

Importance of Data Editing

Make corrections as early as possible, reduce non-response or incomplete answers, eliminate inconsistencies or incorrect info, make the entries clear, legible, and comprehensible, and prepare data for analysis.

Editing Data

Check for duplicate entries and check the totals of each variable if the same as with the sample size.

Spot Checking

compare random questionnaires to the encoded data.

Eyeballing

look for values with no responses or 'not-applicable' responses; check errors for coding

Logic Check

electronically review data.