Statistics: science of collecting, organizing and analyzing data.

Descriptive stats: organizes and summarizes data.

Inferential stats: form conclusions from data.

Sampling Techniques

• Simple random sampling: equal chance of being selected.
• Stratefied sampling: split population into non overlapping groups.
• Systematic sampling: select nth individual, i.e. 8th, 16th, 24th…
• Convenient sampling: only domain experts

Variable types:

• Quantitative: discrete, continous
• Qualitative: categorical

Measurement scales:

• Nominal: categorical data like color
• Ordinal: order matters, i.e. rank of students
• Interval: order and value matter, i.e. interval of temperature
• Ratio:

Frequency distribution: count occurenece

• Histogram: for continous variables
• Bar chart: for discrete variables
• Pdf: smoothing histogram bars into line, probability density function