Statistics Cheatsheet 1



Statisticss Cheatsheet 1

by Lei Bao

Population and Sample

• Population - everything

• Sample - subset

• Parameter (population) & Statistics (sample)

• Census (population data) & Sampling (subset data)

Levels of Measurement (NOIR)

• Nominal - descriptions

• Ordinal - orders

• Interval - numbers without zero

• Ratio - numbers with zero

Types of Data Sampling

• Convenience - due to convenience

• Random - drawing names out of hat

• Systematic - every $n^{th}$

• Cluster - randomly picking groups (smaller) from groups (larger)

• Stratified - randomly picking percentage from each group

	Similarity	Difference
Cluster	Dividing population into groups	Randomly picking group(s) from groups
Stratified	Dividing population into groups	Randomly picking percentage from each group

Shapes of Distributions

• Bell-Shaped (Normal Distribution)

• Skewed Left

• Skewed Right

Descriptive Statistics

• Range

• Mean

• Median

• Mode

• Variance

• Standard Deviation

Empirical Rule

• 68%: $\mu \pm \sigma_x$

• 95%: $\mu \pm 2 \sigma_x$

• 99.7: $\mu \pm 3 \sigma_x$

Regression

• Find regression equations given a set of data

• Make prediction based on the regression equation