Download Lesson 2 in SPSS

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

History of statistics wikipedia, lookup

Taylor's law wikipedia, lookup

Bootstrapping (statistics) wikipedia, lookup

Misuse of statistics wikipedia, lookup

Foundations of statistics wikipedia, lookup

Transcript
Lesson 3 in SPSS
How to find measures variability
using SPSS
The Dataset
• Here’s a nice
dataset.
• We have one
variable called
Age.
• There are 1,514
observations in the
dataset.
First Blush
• To get a quick
picture of this
dataset, let’s
see a
frequency
distribution
histogram
(Lesson 1).
• Hmm,
perhaps a bit
skewed?
Selecting the Analysis
• From the
SPSS menu
bar, choose
• Analyze
• Descriptive
statistics
• Frequencies
Select the Variable(s)
• In the
Frequencies
box, highlight
the variable
age, then click
on the arrow
to pop it into
the Variables
window.
Descriptives Box
• Notice that
when you’ve
done this, the
OK box is
now active.
• But let’s
make sure
we get the
statistics we
want.
Selecting the Statistics
• I’ve selected the
mean, median and
mode as my
measures of central
tendency. Plus, I
asked for the sum.
• For my measures of
spread, I’ve chosen
standard deviation,
variance, and range.
Plus I asked for the
minimum and
maximum values.
The Interquartile Range
• To find the
interquartile range in
SPSS, select
Quartiles.
• I’ve also asked it for a
measure of the
skewness of the
distribution.
• Now click on Continue.
Running the Analysis
• Now we can
click on OK.
The Output
•
•
•
•
So what did we learn?
The mode is 35, the
median is 41.00, and the
mean is 45.63. These
measures appear to be
the perfect definition of a
positively skewed
distribution.
The range is 71 and goes
from a minimum of 18
years to a maximum of 89
years old.
The sample variance is
317.14 and taking the
square root of that we
have the sample standard
deviation of 17.81
Statistics
Age of Res pondent
N
Mean
Median
Mode
Std. Deviation
Variance
Skewness
Std. Error of Skewness
Range
Minimum
Maximum
Sum
Percentiles
Valid
Missing
25
50
75
1514
3
45.63
41.00
35
17.808
317.140
.524
.063
71
18
89
69078
32.00
41.00
60.00
More Output
• To find the interquartile range, we
take the 75th percentile minus the 25th
percentile. Here, it is
60 – 32 = 28. So the
SIQ = 28/2 = 14.
• Also, we note our
skewness value is
.524 with a standard
error of .063. Don’t
worry about that now,
we’ll look at this
again in Lesson 4.
Statistics
Age of Res pondent
N
Mean
Median
Mode
Std. Deviation
Variance
Skewness
Std. Error of Skewness
Range
Minimum
Maximum
Sum
Percentiles
Valid
Missing
25
50
75
1514
3
45.63
41.00
35
17.808
317.140
.524
.063
71
18
89
69078
32.00
41.00
60.00
Visual Representation Median
Mode
• Let’s mark
these on
our graph.
Mean
Mean
SIQ = 14
s = 17.81
Range = 71