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Treat everyone with sincerity, they will certainly appear loveable and friendly.

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Applied Statistics Using SAS and SPSS

Topic: Descriptive Statistics

By Prof Kelly Fan, Cal State Univ, East Bay

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Two Basic Strategies to Explore Data

Begin by examining each variable by itself. Then move on to study the relationship among the variables.

Begin with a graph or graphs. Then add numerical summaries of specific aspects of the data.

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Descriptive Statistics

Displaying data/variables with graphs for categorical (qualitative) variables: Bar plot and Pie chart for quantitative variables: Stemplot and Histogram

Describing data/variables with numbers for categorical (qualitative) variables:

Relative Frequency (Sample Proportion) contingency table

for quantitative variables: to measure center: Mean and Median to measure spread: Interquartile Range (IQR) and Standard

Deviation outliers five-number summary and boxplot scatterplot

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Observed Data: Example 1

Gender Height (inches)

Weight (pounds)

College

M 68.5 155 Sci

F 61.2 99 Bsns

F 63.0 115 Bsns

M 70.0 205 Sci

M 68.6 170 Eng

F 65.1 125 Bsns

M 72.4 220 Eng

M -- 188 Sci

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Controlled Data: Example 2

The tension bond strength of cement mortar is an important characteristic of the product. An engineer is interested in comparing the strength of a modified formulation in which polymer latex emulsions have been added during mixing to the strength of the unmodified mortar. The experimenter has collected 10 observations on strength for the modified formulation and another 10 observations for the unmodified formulation.

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Modified Unmodified

16.85 17.5016.40 17.6317.21 18.2516.35 18.0016.52 17.8617.04 17.7516.96 18.2217.15 17.9016.59 17.9616.57 18.15

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SAS/SPSS Data Input

SPSS: One variable one column in the work sheet

SAS: One variable one name