STAT 350 Exam 1

Probability

Population to sample

Statistical inference

Sample to probability

Estimation, degree of uncertainty

Variable

Unit of measurement

Categorical / qualitative variable

Describe quality, categories, not numerical

Nominal variable

Categorical variables

Simple, no order

Ordinal variables

Categorical variable

With order

Quantitative / numerical variables

Element measured numerically

Discrete variable

Countable number of variables

Continuous variable

Measurements, as precise as possible

Interval scale

No true 0

Can add/subtract to compare, not multiply

Ratio scale

True 0 - represents absence of the value

Perform all operations

Frequency

Count, # of occurrences

Relative frequency

Proportion of cases within a category relative to the total number

(count/total)

Percent distribution

Percentage of cases within the category relative to the total number

100(count/total)

Pie chart

Graph to represent categorical data

Better for data with less conclusion/categories

Bar graph

Represent categorical data or numerical data treated categorically

Histogram

Show distribution with a number line and a certain number of bins

Bins

How many bars in a histogram

Small to medium data = sqrt(#obs), max( round(sqrt(n))+2, 5)

Large data (>400) : between 20 to 30

Modality

Shape, number of peaks

Unimodal

One peak

Bimodal

Two peaks

Multimodal

More than 2 peaks

Skewness

Shape and symmetry to the graph

Negatively skewed

Graph is skewed to the right

Positively skewed

Graph is skewed to the left

Symmetric

Peak is in the middle

Outliers

Datapoints that don’t follow the pattern of the graph