DATA ANALYSIS

Numerical Methods

Measures of
Central Tendency

Mean

The mean is the sume of n numbers divided by n.
The weight of the value is the nº of times a value
appears on the list

Median

Middle value of an ordered list of numbers.

Mode

Number that occurs most frecuently in the list.

Measures of
Position

Quartiles

Percentiles

Measures of
Dispertion

Range

G-L

Interquartile range

Q3 - Q1

Standard deviation

1) Calculate the mean
2) (Value of mean - each nº)2
3) Calculate the mean of differences
4) Possitive square root

*Sample Standard Deviation: Mean of differences
/ n-1.

Example

Example

Graphical Methods

Bar Graphs

Bar Graphs

Segmented Bar Graphs

Segmented Bar Graphs

Bar Graphs with Multiple Variables

Bar Graphs with Multiple Variables

Circle Graphs

Circle Graphs

Histograms

Histograms

r

Histograms are graphs of frecuency distribution; the values are grouped into intervals, each one havinga relative frecuency.

Scatterplot

Scatterplot

r

Scatterplots are used for bivariate data, to show the relationship between two numerical variables. Trend line: overall pattern, slope. Calculated by substracting the G/L of y, and dividing it by G/L of x.

Time Plots

Time Plots

r

Time Plots are used for showing changes in data collected in regular intervals of time.

Positions:
Least (L), Median (M), Greatest (G)

Q1=P25
Q2=M=P50
Q3=75

Example

Example

TUTORIAL