STATISTIC FOR COMPUTING (CSNB293) MODULE 1 GRAPHICAL DATA REPRESENTATION

Variables A variable is a characteristic that may changes under different circumstances Examples: Hair color – varies between individuals White blood cell count – varies between individuals Class schedule – varies between courses Time to failure of a computer component – varies between different computers Transmission error rate – varies between different types of transmission cables, length of cable segment

Basic Statistics Terminologies An experimental unit The individual or object on which a variable is measured. A measurement The results when a variable is actually measured on an experimental unit A population a set of entities concerning which statistical inferences are to be drawn A sample A sub-set of entities drawn from the overall population

Example 1 VariableFirst Year IPTS’s Student Results Experimental UnitStudent MeasurementAbove 3.0 CGPA Between 2.0 and 3.0 CGPA Below 2 CGPA PopulationIPTS’s students SampleUNITEN’s students, MMU students

Graphical Data Representations Data can be represented using graphs / charts. The choice of graph / chart is very much dependent on the nature of data. A single variable measured for different population segments can be graphed using a pie or bar chart. A histogram can be used to illustrate several variables measured for different population segment. A single variable measured over time is called a time series. It can be graphed using a line or bar chart.

Bar Chart Vs. Pie Chart Bar Chart Pie Chart

Histogram

Line Chart SeptemberOctoberNovemberDecemberJanuaryFebruaryMarch CONSUMER PRICE INDEX

Line Chart Vs. Bar Chart LINE CHART BAR CHART

Dotplots Plots the measurements as points on a horizontal axis, stacking the points that duplicate existing points. Example: The set 4, 5, 5, 7,

Stem and Leaf Plots Divide each measurement into two parts: the stem and the leaf. List the stems in a column, with a vertical line to their right. For each measurement, record the leaf portion in the same row as its matching stem. Order the leaves from lowest to highest in each stem. Provide a key to your coding

Example of Stem and Leaf Plots The prices ($) of 18 brands of walking shoes: Reorder

Interpreting Graphs: Location & Spread Where is the data centered on the horizontal axis, and how does it spread out from the center?

Interpreting Graphs: Shapes Mound shaped and symmetric (mirror images) Skewed right: a few unusually large measurements Skewed left: a few unusually small measurements Bimodal: two local peaks

Interpreting Graphs: Outliers Are there any strange or unusual measurements that stand out in the data set? Outlier No Outliers

Example of Interpreting Graphs: Outliers A quality control process measures the diameter of a gear being made by a machine (cm). The technician records 15 diameters, but inadvertently makes a typing mistake on the second entry

STATISTIC FOR COMPUTING(CSNB293) GRAPHICAL DATA REPRESENTATION --END--