Statistics: Data Collection

• Statistics is used in many fields to support scientific research and for decision-making.
• Data is the object of study, so data collection strategies must be carefully selected based on scientific criteria.

Collection of Information: Practical Scenarios

• Data needed for a study are available from different sources.
• Data needed are unavailable and must be collected.

Existing Information

• In the first scenario above, existing information is used, meaning that a researcher or institution gathered data about the same or a similar problem.
• Some institutions collect and publish data on a regular schedule.
• If the data needed are not available, one must define and implement a strategy to obtain them.

Types of Sources

• If the needed information is readily available, there are two types of sources to consider: primary and secondary.
• A primary source refers to the office, person, or agency that publishes or provides the data it has produced.
• This is the original producer of the information.
• A primary source is not necessarily a publication.
• The data have been collected, tabulated, and made available by the collector to be used.
• A secondary source is an office, person, or agency that publishes or summarizes information originally compiled by others.
• Primary sources are recommended when conducting research, as primary sources usually include more detail.
• Primary sources feature less possibility of transcription errors.
• Primary soruces offer definitions of terms and concepts used.
• Primary sources generally provide a copy of the questionnaire.
• Primary sources include a description of the procedures used, an explanation of how the interviewer personnel were trained, and how the data were processed.
• All studies should indicate the source of the data with as much detail as possible.
• If the source must remain undisclosed, it should be labeled as "Source: Confidential."
• Regardless of the source, one must evaluate the quality of the information to be used and assess the sources for quality, comparability, relevance, accuracy, limitations, and applicability to the study or investigation.

Unavailable Information

• When the data are unavailable they can be obtained through observation and questioning.
• Observation is frequently used in social and educational research and can be used in classroom activities for statistics and probability lessons.
• Questioning can be used with observation to supplement collected information, or it can be used independently.

Observation: Advantages

• The information is collected directly, improving the data quality, provided that the observer is well-prepared.
• Observation allows one to describe the facts and simultaneously analyze the situation.
• Observation is critical when conducting experiments of any kind.

Observation: Disadvantages

• Observation requires adequate preparation of the individuals who will conduct the observations to be as natural as possible.
• The person being observed may feel intimidated and not act naturally.
• Standardized data collection instruments are needed for each observation, which may not be easy to establish.

Questioning: Advantages

• Questioning allows one to standardize information for the different statistical units, as all units are asked the same questions.
• Interviewer training does not need to be as detailed as with observation, because the questions are standardized.
• Questioning is adaptable to different situations.

Questioning: Disadvantages

• It is difficult to obtain confidential information, as the interviewee may feel intimidated by the question.
• There is limited possibility to delve deeper into a topic, as the questions are designed to collect very specific information.
• Experimentation is frequently used to collect non-existent information, primarily in probability.
• Experimentation should be a fundamental tool for generating data within the educational system.
• Experimentation harnesses the potential of children and youth and directs it towards learning.
• This technique puts students in real-world scenarios and allows them to develop strategies to argue whether a hypothesis or belief is correct or not.
• The main disadvantage is that the teacher must carefully plan and test the experiments to ensure they achieve their educational purposes.
• Generally experiments are replicated several times to obtain sufficient data to draw well-supported and adequate conclusions.