STA 113 2.0 Descriptive Statistics

Data Collection

Dr. Thiyanga S. Talagala
Department of Statistics, Faculty of Applied Sciences
University of Sri Jayewardenepura, Sri Lanka

Primary vs Secondary Data

Primary Data

  • Primary data refers to information collected directly by the researcher.

  • This data is gathered specifically to address the researcher’s current problem or objective, tailored to meet the specific requirements of a particular study.

Secondary Data

  • Secondary data refers to information that has already been collected, compiled, and published by others for purposes different from the researcher’s current study.

Methods of collecting primary data

  • surveys

  • census

  • interviews

  • observational studies

  • experimental studies

  • case studies

  • content analysis

  • ethnography

  • surveillance

  • focus groups

  • analyse social media content

Observational Studies vs Experimental Study

Observational Studies vs Experimental Study: Examples

Investigate the effect of fertilizer A and B on chili crop yield.

Researcher 1

Step 1: Population: Identify two groups of chili farmers based on the fertilizer they use.

Group A: Farmers using fertilizer A.

Group B: Farmers using fertilizer B.

Step 2: Data collection: Collect data on chili crop yield from both groups at the end of the growing season.

Researcher 2

Step 1: Randomization: Randomly assign plots of land to receive either fertilizer A or fertilizer B. Same seed variety is used.

Step 2: Control Conditions: Ensure all other conditions (water, sunlight, humidity, soil type) are kept constant across all plots. Use consistent pest management practices and ensure uniform planting and harvesting techniques.

Step 3: Data Collection: Measure the chili crop yield from each plot at the end of the growing season.

Researcher 1

In-class demo:

Researcher 2

In-class demo:

Source: https://www.greenproventures.com/guide-to-starting-greenhouse-farming-with-shade-nets/

Methods of collecting secondary data

  • Online databases: These databases can be categorized into two main types based on their accessibility: commercial and open-access.

Ex: Department of Census and Statistics website: http://www.statistics.gov.lk/#gsc.tab=0

Ex: Open-access: Dengue data hub: https://denguedatahub.netlify.app/

  • Government and Institutional Reports

Ex: Annual Report, Central Bank of Sri Lanka

Methods of collecting secondary data (cont.)

  • Commercial Data: Purchasing or accessing data from commercial sources like market research firms, industry reports, and business analytics services

  • Census and Public Records: Using demographic data, economic statistics, and other information from national censuses and public records maintained by government agencies.

  • Media Archives: Reviewing newspapers, magazines, television broadcasts, and other media sources for relevant historical data and trends.

Methods of collecting secondary data (cont.)

  • Internal Company Records: Examining an organization’s internal reports, financial statements, sales records, and other documents for business research purposes.

  • Libraries and Archives: Visiting physical or digital libraries and archives to access a wide range of historical documents, manuscripts, and archival records.

  • Meta-Analysis: Synthesizing data from multiple studies to draw broader conclusions, often used in scientific and medical research.

Why Secondary Data?

  1. Cost-Effective (not always)

  2. Time-Saving

  3. Preliminary Research: It serves as a valuable resource for preliminary research or background studies, helping to identify gaps in knowledge, formulate hypotheses, and refine research questions.

  4. Historical Analysis: Enables researchers to conduct historical analyses and understand past trends, events, and behaviors, which can inform present and future research directions.

  5. Validation: Secondary data can be used to validate findings from primary data

Your Turn

Find advatages and disadvatages of using primary and secondary data.

True or False?

Question 1

In an observational study, researchers directly intervene and manipulate variables to observe their effects on the outcome.

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Question 2

The sample in a study refers to the entire group of individuals or objects that researchers want to study.

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Question 3

Descriptive statistics are used to make inferences and predictions about a population based on sample data.

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Question 4

Inferential statistics are used to summarize and describe the characteristics of a dataset.

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Question 5

The sample in a study represents the entire group of individuals or objects that researchers want to study.

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Question 6

Descriptive statistics are used to make predictions about a population based on sample data.

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Question 7

If there is no data, statistical analysis can still be performed based on theoretical assumptions.

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Question 8

Primary data is collected through methods such as surveys, interviews, and experiments.

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Question 9

Primary data collection allows researchers to have more control over the data quality and reliability.

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Question 10

Secondary data sources may include government databases, archival records, and proprietary datasets.

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