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Introduction to SPSS
Ashu S. Kedia
Lecturer, Dept. of Civil Engineering,
School of Technology,
PDPU, aisan, !andhinagar
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• SPSS is a software package used for conducting statistical
analysis, manipulating data, and generating table and graphs
that summarize data.
• SPSS performs statistical analysis range from basic descriptive
statistics to advanced inferential statistical, such as regressionmodel, analysis of variance (Anova), factor analysis etc.
• SPSS also contains several tools for manipulating data,
including functions for recording data, macros programming onvisual basic editor, merging data, and aggregating comple
data sets.
Introduction
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A scientist, an engineer, an economist or a physician is interested
in discovering about a phenomenon that he assumes or believes toeist.
!hatever phenomenon that he desires to eplain, he tries to
eplain it by collecting data from the real world and then using
these data he draws conclusions.
"he available data are analyzed with the help of statistical tools
by building statistical models of the phenomenon.
Introduction
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#iologist $ finding the effect of a certain drug on rat metabolism
Psychologist $ discover the process that occur in all human beings
%conomist $ building a model that apply to all salary groups
Population And Sample
Population
Sample
&mpossible $ to study the entire unit
Practical $ to study a handful of observations, draws conclusions on
entire unit.
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Population refers to all possible observations that can be made on a specific
characteristic.
'or a biologist, the term population could mean all the rats now living and all rats
yet to be born or it could mean all rats of a certain species now living in a specific
area.
#iologist cannot collect data from every rat and the psychologist cannot collect data
from every human being. "herefore, he collects data from a small subset of the
population known as sample and use these data to infer on the population as a
whole.
&f engineers want to build a dam, they cannot make a full*size model of the dam theywant to build+ instead they build a small scale model and tests this model under
various conditions. "hese engineers infer how the full*sized dam will respond from
the results of the small*scale model.
"herefore, in real life situations we never have access to the entire population, so wecollect smaller samples and use the characteristics of the sample to infer the
characteristics of the population.
"he larger the sample, the more likely it is to represent the whole population. &t is
essential that a sample should be representative of the population from which it isdrawn
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Observations and Variables
&n statistics, we observe or measure characteristics called variables. "he study
subects are called observational units.
'or eample, if the investigator is interested in studying the household income
and household size among - families, the //& and //S are the variables, the
//& and //S values are the observations and the families are the observational
units.
&f the investigator records the family0s vehicle ownership, number of working
members, number of students in addition to //& and //S, then he has a data setof - families with observations recorded on each of five variables (//&, //S,
12, 3!4, 3%4) for each family or observation unit.
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Variables and Scales
5uantitative or 4easurement 1ariable on &nterval Scale
"here are numerous characteristics found in the world which can be measured in
some fashion. Some characteristics like height, weight, temperature, salary etc. are
6uantitative variables.
Since these variables are capable of eact measurements and assume, at least
theoretically, infinite number of values between any two fied points. "he data
collected on such measurements are called continuous data and we use interval scale
for these data. 'or eample, height of individuals can be fied on some interval like 7*
8, 8*9, 9*: feet.
2n the other hand, number of children in a family can be counted as ,-,7,8,.. and the
number of families having these many children can be counted and given. /ere the
number of children is -,7,8,.. and not any intermediate value as -.: or 7.8. Such a
variable is called discrete variable.
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Variables and Scales
5ualitative 1ariable on 3ominal Scale
• /ere the units are assigned to specific categories in accordance with certain
attributes. 'or eample, gender is measured on a nominal scale, namely male and
female.
• 5uantitative variable is an attribute and is descriptive in nature. 'or eample,
colour of a person like fair, whitish and dark.
;anked 1ariable on 2rdinal Scale
Some characteristics can neither be measured nor counted, but can be either ordered
or ranked according to their magnitude. Such variables are called ranked variables.
/ere the units are assigned an order or rank. 'or eample, income of the people can
be categorized as low income, middle income and high income. "he only re6uirement
is that the order is maintained throughout the study.
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SPSS looks a lot like a typical spreadsheet application. Spreadsheets, on the other
hand, are capable of a lot of things that SPSS is good at, like generating graphs and
statistics on a data set.
• Spreadsheets are designed to be very fleible and broadly applicable to manydifferent tasks, while SPSS was designed specifically for statistical processing
of large amounts of data at an enterprise level.
• 'or eample, unlike a spreadsheet, SPSS has the concepts of case and
variable built in. "he rows in SPSS always represent cases, for eample
survey responses or eperimental subects, and the columns always representvariables observed from those cases, like the specific values given by the survey
respondents.
•
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Strengths
• 1ery robust statistical software
• 4any comple statistical tests available
• >ood stats coach help with interpreting results
• %asily and 6uickly displays data tables
•
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4any commercial products available SAS, Statistica, 4initab,
and others
Excel
!idely available (part of 4S 2ffice Suite) 3ot a statistical
software $ spreadsheet
'inance, math, and statistics applications
SPSS
;obust software for sophisticated statistical applications
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Applications of SPSS
"ransportation 4odelling
4edical Sciences
4anagement
Social Sciences
Types of Variables
=iscrete 1ariables
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SPSS ATA !ILE
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SPSS ATA !ILE
• 2pening a =ata file in SPSS
•
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SPSS ata Editor
"wo spreadsheets like an array
=ata %ditor 1ariable 1iew B =ata 1iew
=ata 1iew $ new data is entered
1ariable 1iew $ contains the names and details of the variables of
the data.
Status #ar $ SPSS Processor is ready=ata is typed directly in the SPSS data file created already in the
=ata %ditor
=ata can also be imported from the %cel and Statistica
SPSS $ %ach row represents only one case and each column
represents a variable or a character of the case measured.
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SPSS ata Editor
"wo spreadsheets like an array
=ata %ditor 1ariable 1iew B =ata 1iew
=ata 1iew $ new data is entered
1ariable 1iew $ contains the names and details of the variables of
the data.
Status #ar $ SPSS Processor is ready=ata is typed directly in the SPSS data file created already in the
=ata %ditor
=ata can also be imported from the %cel and Statistica
SPSS $ %ach row represents only one case and each column
represents a variable or a character of the case measured.
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SPSS Variable Vie"
"wo spreadsheets like an array
=ata %ditor 1ariable 1iew B =ata 1iew
=ata 1iew $ new data is entered
1ariable 1iew $ contains the names and details of the variables of
the data.
Status #ar $ SPSS Processor is ready=ata is typed directly in the SPSS data file created already in the
=ata %ditor
=ata can also be imported from the %cel and Statistica
SPSS $ %ach row represents only one case and each column
represents a variable or a character of the case measured.
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Variable Vie"# etails
3ameC string character (normally letters and spaces, and sometimes
digits). &t appears at the head of a column in =ata 1iew but not in the
output. &t is a shortened view that appears only within the data view. &tshould be a continuous se6uence with no space. "hough D9 letters can
be entered it is desirable to keep it short.
"ypeC &t accepts eight different types of variables. "wo important onesare the numeric, i.e., numeral with decimal point
and string, i.e., names of participants, cities or any non*numeric
characters.
!idthC &t is the width of the variable. =efault setting for the width of
the variable is E. %dit $ options $ =ata.
=ecimalsC &t is the number of decimals that will be displayed in the
=ata 1iew. =efault is 7.
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Variable Vie"# etails
FabelC is a meaningful phrase with spaces in between words. &t
describes the variable and also appears in the output. &t is important to
assign meaningful labels for the variables.
1aluesC "his column is meant for grouping variables. &t gives the keys
to the meanings of code numbers. "he value dialog bo is opened by
clicking the grey area. "he value and value labels are given in thevalue dialog bo.
4issing 1alueC &t specifies the missing values in a data set.