STATS 1123 - Descriptive Statistics

vocab: subjects

refer to the things we are interested in

• need to specify n

vocab: variable

direct characteristics of the subject (e.g. height)

vocab: measurements

the process we use to assign numbers, letters, or words to various of elements

vocab: observations

set of measurements obtained for a particular element

**NOTE: sample size = # of subjects = n

scales of measurement

numerical:

• interval/ratio scale

categorical:

• ordinal (order)

• nominal (no order)

categorical graphs

• bar graph → good for ordinal

• pie chart

numerical graphs

• histogram

• stem-and-leaf plot / stemplots (need scale)

• boxplot

• scatterplot

• side-by-side bar chart

historgram descriptions

• centre

• spread

• shape (uni / bi -modal / symmetric / bell / skewed)

• outlier

cumulative distributions

• cumulative frequency (number)

• cumulative relative frequency (decimal)

• cumulative percent (percentage)

pg.14

numerical summaries

• mean (average) → not resistant

• median (middle) → resistant

• mode (most frequent)

measure of spread

• range

• standard deviation

formula for finding the median number

sample proportion

Xth quartile form

how to find the quartiles (Q1, Q2, Q3)

• Q1 - median of the lower half

• Q2 - median for the entire data

• Q3 - median for the upper half

finding pth quartile formula

how to calculate for outliers for boxplot

standard deviation formula

IQR formula