Arthimetic mean for population :

Arthimetic mean for sample:

Central Tendency: determine the center of distribution of data.

• Mean
• Median
• Mode

Measure of dispersion: how spread the data distribution is.

• Variance: to know how spread data is
  • For population

• • For sample

• Standard deviation: root of variance. To measure how far a value is from the mean

• Percentile: a value at x% means x% of the distribution is below it (less than the value).

  • % = #values count below value / #total values count
  • At x%: whats the value? Calculate index of value.

  

  • If index is decimal:

  

Five number summary:

• Minimum
• First quartile (Q1): 25%
• Median
• Third quartile (Q3): 75%
• Maximum

Interquartile range (IRQ): Q3 - Q1

To find outliers: find lower fence and upper fence, any value above upper and below lower fence is an outlier: