Introduction to Statistics

A researcher is studying the effectiveness of a new drug on reducing blood pressure. They collect blood pressure readings from a group of patients before and after administering the drug. Which type of data are the blood pressure readings?

In a survey, respondents are asked to rate their satisfaction with a product on a scale of 'Very Dissatisfied,' 'Dissatisfied,' 'Neutral,' 'Satisfied,' and 'Very Satisfied.' Which level of measurement does this represent?

A quality control inspector is examining a batch of manufactured items. They record the number of defective items in each batch. What type of data is the number of defective items?

A marketing team wants to understand the preferred web browser (e.g., Chrome, Firefox, Safari) used by their website visitors. They collect data on the browser type used by each visitor. What type of data is the browser type?

A university wants to analyze the distribution of students across different majors. Which of the following constitutes the population in this scenario?

Population (in statistics)

Sample (in statistics)

Statistics is a field of mathematics that involves collecting, analyzing, interpreting, and presenting numerical data.
Statistics provides methods and tools to summarize, organize, and interpret data.
Statistics enables people to make informed decisions or draw conclusions from the information available.

Important Definitions

Population represents the complete collection of all elements under consideration.
Sample refers to a subject of individuals, items, or data points selected from a larger population.
Data refers to factual information or observations that are collected, measured, or recorded.
Variable is a characteristic or quantity that can take different values, usually observed and measured in a study or an experiment.

Types of Data

Categorical (Qualitative) data refers to information that is non-numerical and categorical in nature.
- Examples include colors, types of animals, opinions, and feelings.
Numerical (Quantitative) data refers to information that is measured and expressed in numerical form or quantities.
- Discrete data consists of values that are distinct and separate, usually in whole numbers.
- Continuous data can take any value within a certain range and can be measured with precision.
  - Examples include height, weight, and temperature

Four Levels of Measurements

Nominal Level: consists of categories or labels with no numerical significance.
- For example, gender.
Ordinal Level: have specific order/ranking.
- The categories are distinct, they also have a relative position or rank in relation to one another.
- For example (1st, 2nd, 3rd) and (poor, fair, excellent).