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Find the Mean and Standard Deviation in SPSS for Two Groups - YouTube
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In this tutorial we're going to take a
look at how to obtain means for
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different groups of a variable on some
other variable of interest.
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Let me show you what I mean here. So, for
example, in this data set, we have two
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variables, play golf and satisfaction. Now
play golf is coded, if I click on my
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Value Labels button here, I've already
coded it, and you can see that we have
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either yes,
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those who do play golf, or no, those who
do not play golf. Now when I said I
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wanted to obtain means for the different
groups,
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what I want is I want to get a mean on
satisfaction this variable for golfers,
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for those who answer yes to playing golf,
I want a mean for this group alone, and
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then I want to mean for the no group as
well.
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OK and this variable satisfaction, higher
scores indicate greater satisfaction. And
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these are 7 people who lived in the
community in which there was a golf
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course on it.
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So 5 of the people who lived in the
community who answered yes, they're
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golfers, and the 2 who answered no, they
are not golfers.
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OK so once again I want satisfaction, a
mean satisfaction level, separately for
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the yes group and one for the no group;
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I want it separated. OK and this is often
area of confusion in SPSS, how to do
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this.
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Let's go ahead and proceed with perhaps
a normal route of trying to figure this
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out. Go to Analyze, Descriptive
Statistics, Descriptives, and we're going
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to see what happens if we just go ahead
and do an analysis directly on
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satisfaction. OK so I'm going to move
satisfaction over,
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go to Options, and then I want the Mean
and let's get the Standard Deviation as
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well for this lesson, so I'll be deselect
Minimum and Maximum. Click Continue and
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click OK. Our output or viewer window
opens
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and notice here in our Descriptive
Statistics, recall that I said that I
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wanted means separately for the yes
group and the no group. But if you notice
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this output here, I have satisfaction
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all 7 people are included, and I have
just one overall mean of 7.86, so this
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actually didn't give me means for the
different groups. I don't have a mean for
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the yes and a mean for the no
groups.
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I just have an overall mean. So this
actually didn't do what I wanted.
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So let's go try again. Let's click on
this little star here, this
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this will take you straight to the data.
And, once again, I want a mean for just
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the yes group, the 1s, and a mean
for just the 2, the No's. And I wanted to
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show you the Descriptives way just to
show you that it's not actually correct,
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and why it's not. So now we know what we
want,
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we want the means broken down separately
by the different groups. To do that we
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need to go to Analyze, Compare Means,
Means. OK so select that and then here in
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our Dependent List,
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this is where the satisfaction variable
would go, so move that over. And the
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Independent List will always be the
categorical variable, in this case the
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variable, play golf.
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It's categorical and it happens to be
dichotomous because there are only two
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options, a 1 or a 2, or a Yes
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or No. OK so play golf will go to the
Independent List and then go to Options,
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so we can see what options are selected.
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I see a mean and I see a standard
deviation by default and number of cases
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as well. We can keep number of cases, that
could be helpful, but let's drag that up
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to the top here and have that present
first in our output. OK so
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everything looks good here.
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Let's click Continue and then click OK.
Now our output opens
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we're going to scroll down here, actually
I'm going to delete a little bit of this.
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I'll delete this by selecting it,
pressing the Delete key. I'm going to
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delete this here, so we can see these two
tables at the same time.
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Here's the output of my Means procedure,
the procedure we just ran.
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I'm just going to briefly mention this
Case Processing Summary table, just to
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say it shows that all 7 observations
were included, and none were excluded, so
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everything was analyzed, that's all that
means.
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Zeroing in on this table, the Report table,
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this is what we want to see. Notice here
I have the play golf variable and I have
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analyses for the Yes group the 5
people who were in the Yes group, and the
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No group, the two people in that group.
And notice now I have means broken down
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separately for these two groups, which is
exactly what I wanted.
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So the yes group, those who play golf, had
an average satisfaction score of 8.20,
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whereas those who did not play golf had
an average satisfaction score of 7.00.
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So you should be able to see, at least in
the sample here, that those who played golf
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did have a higher average satisfaction
score, or higher mean satisfaction score,
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than those who did not play golf. OK and we
see the standard deviations here as well.
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Just as a side note this standard
deviation is 0 because our two people
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who were in the No group both had a
score of 7.
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If they both have a score 7, there's
no variability at all in the data set for
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this group.
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So that's why we have a standard
deviation of 0. One last note here.
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Notice the Total. See where it says
7 here, and then we have a mean of
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7.86 standard deviation .90? If we go
back up here to our original analysis,
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the analysis using Descriptive
Statistics and then using the
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Descriptives option,
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notice we have the same thing: 7.86 for
the mean .90 for the standard
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deviation.
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So what the Means procedure does down
here
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it breaks it down by the different
groups, and it also gives you the overall
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analysis down here, which is what we got
the first time by Descriptive Statistics.
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But anytime you want to get a mean, a
descriptive analysis, but of means
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separately for different groups, you want
to go to Analyze, Compare Means and then
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the Means procedure. Now if you're doing
inferential analyses, like a two-way
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ANOVA, for example, you can get that
within the two-way ANOVA procedure.
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But if we're just doing simple
descriptive statistics, no inferential
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testing, and we just want to see means
here by different groups then you want
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to use Analyze, Compare Means, Means. This
concludes the tutorial on using the
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Means procedure in SPSS.
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