CHAPTER 34 Collection and Organisation of Data

PRIMARY AND SECONDARY DATA PRIMARY DATA is collected by an individual or organisation to use for a particular purpose. PRIMARY DATA is obtained from experiments, investigations, surveys and by using questionnaires. SECONDARY DATA is already available or has been collected by someone else for different purpose. Sources of SECONDARY DATA include the Met Office and the Internet. Data which can only be DESCRIBED in WORDS is QUALITATIVE e.g make of car, colour of hair, etc. Data which is given NUMERICAL VALUES is QUANTITATIVE. QUANTITATIVE data is either DISCRETE or CONTINUOUS. DISCRETE data can only take certain values e.g shoe size, number of students in a class etc. CONTINUOUS data can take any value depending on how accurately it is measured eg foot length, height, weight, temperature etc.

COLLECTION OF DATA Data can be collected in a variety of ways e.g by observation, interviewing people and questionnaires. The method of collection will often depend on the type of data to be collected. DATA COLLECTION SHEETS are used to record data, normally using a TALLY TABLE. The total number of times each data item appears is called its FREQUENCY. A table for data with the totals included is called a FREQUENCY DISTRIBUTION. For large amounts of DISCRETE data, or for CONTINUOUS data, the data is organised into GROUPS or CLASSES. When data is collected in GROUPS it is called a GROUPED FREQUENCY DISTRIBUTION and the GROUPS the data is put into are called CLASS INTERVALS.

QUESTIONNAIRES When constructing questions for a questionnaire you should: 1. Use simple language, so that everyone can understand the question 2. Ask short questions which can be answered with ‘Yes’ or ‘No’, a number, or a response from multiple choices provided. 3. Provide tick boxes so that questions can be answered easily. 4. Avoid OPEN ENDED questions which would produce answers that would be too difficult to analyse. 5. Avoid LEADING QUESTIONS which would produce BIASED answers 6. Ask questions in a logical order.

HYPOTHESIS A HYPOTHESIS is a statement that may or not be true.

SAMPLING When information is required about a large group of people it is not always possible to survey everyone and only a SAMPLE may be asked. The SAMPLE chosen should be large enough to make the result meaningful and representative of the whole group or the result may be BIASED. The result of a survey may also be BIASED if there is any form of deliberate selection or if the sample is incomplete.