0:00:00.000,0:00:03.060
>> So here we are in SPSS.

0:00:03.060,0:00:04.900
I have created a junk data

0:00:04.900,0:00:07.220
set just to help[br]illustrate how we can

0:00:07.220,0:00:08.840
compute variables[br]or compute

0:00:08.840,0:00:09.980
new variables using

0:00:09.980,0:00:12.010
the values from[br]existing ones.

0:00:12.010,0:00:14.140
This is a pretty[br]straightforward process.

0:00:14.140,0:00:15.280
It looks a little bit

0:00:15.280,0:00:16.680
different than things[br]that we've done

0:00:16.680,0:00:18.580
before or other[br]ways that we're

0:00:18.580,0:00:20.640
going to be using[br]SPSS in this course.

0:00:20.640,0:00:22.440
So it might look a[br]little bit different,

0:00:22.440,0:00:23.980
but it is pretty[br]straightforward and

0:00:23.980,0:00:26.375
pretty easy once you[br]know how to do this.

0:00:26.375,0:00:27.740
So the first[br]thing that we'll

0:00:27.740,0:00:29.345
do is go to Transform,

0:00:29.345,0:00:30.680
and then the[br]first option we

0:00:30.680,0:00:32.120
have there is[br]compute variable.

0:00:32.120,0:00:34.440
So click on that. We get

0:00:34.440,0:00:36.165
this new window[br]that pops up.

0:00:36.165,0:00:37.800
The first thing[br]that we really want

0:00:37.800,0:00:39.340
to look at is in[br]the top left,

0:00:39.340,0:00:42.580
and that's this target[br]variable window.

0:00:42.580,0:00:44.130
Basically what[br]the computer

0:00:44.130,0:00:45.610
is asking you is to create

0:00:45.610,0:00:47.630
a name for the[br]new variable

0:00:47.630,0:00:49.070
that you're going[br]to be computing.

0:00:49.070,0:00:50.860
This name needs[br]to be unique,

0:00:50.860,0:00:53.170
it's one that can't[br]have spaces in it,

0:00:53.170,0:00:55.315
and it should avoid[br]special characters.

0:00:55.315,0:00:56.710
But, in this case,

0:00:56.710,0:00:58.630
what I like to[br]do is include

0:00:58.630,0:01:01.330
some piece of[br]information in there

0:01:01.330,0:01:03.550
in the naming[br]convention I use that

0:01:03.550,0:01:04.810
helps me know what this is

0:01:04.810,0:01:06.250
just by looking at it.

0:01:06.250,0:01:07.890
So what we're going[br]to be doing is

0:01:07.890,0:01:09.650
we're going to be[br]summing items 1,

0:01:09.650,0:01:10.970
2, 3, 4, 5,

0:01:10.970,0:01:12.740
and 6 together, adding[br]those together.

0:01:12.740,0:01:14.330
So an easy way[br]to do that is

0:01:14.330,0:01:17.480
just to put sumofitems.

0:01:17.480,0:01:20.040
That way, when I look at

0:01:20.040,0:01:21.850
this new variable[br]once it's generated,

0:01:21.850,0:01:23.350
I know that that's[br]the variable

0:01:23.350,0:01:24.930
that I really want[br]to be working

0:01:24.930,0:01:26.720
with or running[br]my tests on

0:01:26.720,0:01:28.030
because that contains

0:01:28.030,0:01:29.865
the information from[br]the other ones.

0:01:29.865,0:01:32.970
You can click on[br]Type & Label.

0:01:32.970,0:01:36.390
The label is the more[br]drawn-out explanation.

0:01:36.390,0:01:37.870
That's one that[br]you can include

0:01:37.870,0:01:39.390
additional characters or

0:01:39.390,0:01:41.070
spaces and special[br]characters.

0:01:41.070,0:01:43.150
In our case, I'm[br]going to put this is

0:01:43.150,0:01:48.975
the sum of items[br]1 through 6.

0:01:48.975,0:01:50.790
And that way I know that

0:01:50.790,0:01:52.550
that is going to give me

0:01:52.550,0:01:55.150
a more drawn-out[br]explanation

0:01:55.150,0:01:57.010
of what this[br]variable includes.

0:01:57.010,0:01:59.325
We know this is[br]going to be numeric.

0:01:59.325,0:02:01.175
So click Continue.

0:02:01.175,0:02:03.110
The next thing we're[br]going to look at

0:02:03.110,0:02:05.045
is this numeric[br]expression box.

0:02:05.045,0:02:06.530
And will actually[br]come back

0:02:06.530,0:02:07.730
to this in just a minute,

0:02:07.730,0:02:08.390
but this is where you're

0:02:08.390,0:02:09.330
going to be doing most

0:02:09.330,0:02:11.390
of the work when you're[br]computing a variable.

0:02:11.390,0:02:13.190
What you'll want[br]to go to next

0:02:13.190,0:02:14.880
is this function[br]group area.

0:02:14.880,0:02:16.665
So I'm going to[br]click on All.

0:02:16.665,0:02:18.630
And you notice right[br]below it we've

0:02:18.630,0:02:20.580
got these functions[br]and special variables,

0:02:20.580,0:02:22.815
and this popped up[br]when I clicked on All.

0:02:22.815,0:02:24.550
This has a whole bunch of

0:02:24.550,0:02:26.200
different pre-existing[br]functions,

0:02:26.200,0:02:27.640
so you don't need to[br]reinvent the wheel,

0:02:27.640,0:02:28.870
you can basically use

0:02:28.870,0:02:30.950
these pre-existing[br]functions to

0:02:30.950,0:02:33.135
help you compute[br]this new variable.

0:02:33.135,0:02:34.710
I'm going to go[br]down to sum,

0:02:34.710,0:02:36.250
and these are in[br]alphabetical order,

0:02:36.250,0:02:37.890
so it's pretty[br]easy to find.

0:02:37.890,0:02:40.180
Here we have sum, and[br]when I click on sum,

0:02:40.180,0:02:41.490
you'll notice[br]that this box on

0:02:41.490,0:02:43.955
the left populated[br]with some text.

0:02:43.955,0:02:46.005
This box is actually[br]pretty useful.

0:02:46.005,0:02:47.650
So the first thing[br]it shows you is

0:02:47.650,0:02:48.570
an example of what

0:02:48.570,0:02:50.210
this expression[br]is going to be.

0:02:50.210,0:02:51.540
And our expression[br]sounds like

0:02:51.540,0:02:52.635
a really fancy term.

0:02:52.635,0:02:54.050
If you've ever[br]used a formula

0:02:54.050,0:02:55.670
in Excel, it's[br]basically that.

0:02:55.670,0:02:56.990
It's telling the computer

0:02:56.990,0:02:58.465
what it needs to do.

0:02:58.465,0:03:00.750
In this case,[br]just like Excel,

0:03:00.750,0:03:02.030
we've got the word sum,

0:03:02.030,0:03:03.570
which tells the computer[br]it's going to be

0:03:03.570,0:03:05.365
summing different[br]values together,

0:03:05.365,0:03:06.630
and then in parentheses,

0:03:06.630,0:03:07.570
immediately after that,

0:03:07.570,0:03:09.070
we have different[br]variables

0:03:09.070,0:03:10.705
that are separated[br]by a comma,

0:03:10.705,0:03:11.930
and that's what tells the

0:03:11.930,0:03:13.390
computer to add x, y,

0:03:13.390,0:03:15.150
and z things[br]together to create

0:03:15.150,0:03:17.800
a new variable or[br]compute a new variable.

0:03:17.800,0:03:18.870
This also provides

0:03:18.870,0:03:20.750
additional extra[br]content here,

0:03:20.750,0:03:22.190
but we don't need to[br]worry about that.

0:03:22.190,0:03:23.930
I found this is[br]helpful if you

0:03:23.930,0:03:26.000
are stuck or something[br]isn't working right.

0:03:26.000,0:03:27.930
So we've got sum selected,

0:03:27.930,0:03:29.780
we're going to be[br]summing the items of 1,

0:03:29.780,0:03:31.760
2, 3, 4, 5, and[br]6 together.

0:03:31.760,0:03:33.055
We've got that selected.

0:03:33.055,0:03:34.110
So the next thing you do

0:03:34.110,0:03:35.190
is click this up arrow,

0:03:35.190,0:03:36.270
which basically takes

0:03:36.270,0:03:38.030
that pre-existing function

0:03:38.030,0:03:39.720
and it kicks it up[br]to this numeric

0:03:39.720,0:03:41.550
and expression box.

0:03:41.550,0:03:43.870
The next thing that[br]we're going to do,

0:03:43.870,0:03:44.710
we've already told

0:03:44.710,0:03:45.810
the computer[br]that we're going

0:03:45.810,0:03:47.740
to sum different[br]variables together,

0:03:47.740,0:03:48.910
we need to tell it which

0:03:48.910,0:03:50.480
variables to sum together.

0:03:50.480,0:03:52.790
So the easy way[br]to do this is to

0:03:52.790,0:03:54.110
click on the first

0:03:54.110,0:03:55.445
item that you[br]want to include,

0:03:55.445,0:03:57.850
and you'll notice[br]that this arrow

0:03:57.850,0:03:59.290
switch sides from pointing

0:03:59.290,0:04:00.785
to the left to[br]pointing to the right,

0:04:00.785,0:04:02.060
click over 1,

0:04:02.060,0:04:04.350
and we've already[br]moved over item 1.

0:04:04.350,0:04:07.020
What you need to be[br]careful of is that you

0:04:07.020,0:04:09.640
always have a comma[br]after each variable,

0:04:09.640,0:04:11.085
except for the last one.

0:04:11.085,0:04:12.600
So a comma is[br]already here,

0:04:12.600,0:04:14.815
but what I usually do[br]is I just hit a comma,

0:04:14.815,0:04:16.675
I go to item 2,

0:04:16.675,0:04:19.010
kick that over, comma,

0:04:19.010,0:04:21.030
item 3, kick that over,

0:04:21.030,0:04:23.550
comma, item 4,[br]kick that over,

0:04:23.550,0:04:25.260
comma, item 5,

0:04:25.260,0:04:26.880
kick that over, comma,

0:04:26.880,0:04:28.935
item 6, kick that over.

0:04:28.935,0:04:30.420
Now, we know that item 6

0:04:30.420,0:04:31.920
is the last one we have,

0:04:31.920,0:04:33.690
the last variable[br]we're including,

0:04:33.690,0:04:35.100
so what we're[br]going to do is

0:04:35.100,0:04:36.700
just delete out[br]that question mark,

0:04:36.700,0:04:38.515
we're going to delete[br]out that last comma,

0:04:38.515,0:04:40.260
and then if we read[br]through this real quick

0:04:40.260,0:04:40.980
just to make sure we

0:04:40.980,0:04:42.190
don't have any problems,

0:04:42.190,0:04:45.095
we've got creating[br]sumofitems,

0:04:45.095,0:04:46.880
this is going to[br]be the sum of

0:04:46.880,0:04:48.435
item 1, 2, 3,

0:04:48.435,0:04:51.280
4, 5, and 6,

0:04:51.280,0:04:54.095
and what we're going[br]to do now is click OK.

0:04:54.095,0:04:56.620
An output window pops

0:04:56.620,0:04:57.720
up and it basically tells

0:04:57.720,0:04:58.860
you what the computer did.

0:04:58.860,0:05:00.500
It computed the[br]sum of items,

0:05:00.500,0:05:01.830
which was the[br]sum of item 1,

0:05:01.830,0:05:03.315
2, 3, 4, 5, and 6,

0:05:03.315,0:05:05.110
it gives us the[br]variable label,

0:05:05.110,0:05:08.620
it gives us that[br]descriptive text I put in.

0:05:08.620,0:05:10.080
I'm just going to[br]minimize this window,

0:05:10.080,0:05:11.280
and if we look back here,

0:05:11.280,0:05:12.200
you might notice that

0:05:12.200,0:05:13.620
there's this new column,

0:05:13.620,0:05:15.510
this new variable,[br]that sumofitems,

0:05:15.510,0:05:16.935
that wasn't there[br]when we started,

0:05:16.935,0:05:19.155
and that's because[br]SPSS computed that.

0:05:19.155,0:05:20.780
And if we add[br]these together,

0:05:20.780,0:05:22.235
if you add each row,

0:05:22.235,0:05:24.320
we've got 1, 2, 1, 3, 5,

0:05:24.320,0:05:26.565
1, that adds to 13,

0:05:26.565,0:05:28.005
5, 1, 2,

0:05:28.005,0:05:29.940
3, 5, 1 adds to 17.

0:05:29.940,0:05:31.540
So it's done that[br]math for us.

0:05:31.540,0:05:33.425
We didn't have to[br]manually do it.

0:05:33.425,0:05:35.720
I know, yes, it'd[br]be pretty easy to

0:05:35.720,0:05:38.280
manually do this[br]for 10 cases,

0:05:38.280,0:05:41.060
but if you have a dataset[br]that has 500 cases,

0:05:41.060,0:05:43.000
that would be very[br]time-consuming to do.

0:05:43.000,0:05:45.460
And you could see[br]that this function of

0:05:45.460,0:05:47.360
computing this[br]variable can

0:05:47.360,0:05:48.460
save you a lot of time.

0:05:48.460,0:05:49.820
It's also more accurate.

0:05:49.820,0:05:51.385
It's going to[br]take any error

0:05:51.385,0:05:53.790
out of the equation.

0:05:53.790,0:05:54.940
And we know that often

0:05:54.940,0:05:56.120
when we do things by hand,

0:05:56.120,0:05:57.900
we can introduce[br]error into things,

0:05:57.900,0:05:59.550
so we want to avoid that.

0:05:59.550,0:06:01.845
That's one way to[br]computer a variable.

0:06:01.845,0:06:04.760
I'm going to show[br]you a different type

0:06:04.760,0:06:06.160
of variable that[br]we can compute.

0:06:06.160,0:06:07.845
I'm going to go[br]back to Transform,

0:06:07.845,0:06:09.570
I'm going to go back[br]to Compute Variable.

0:06:09.570,0:06:11.420
I'm actually going[br]to clear this out.

0:06:11.420,0:06:12.860
We're done with[br]someofitems,

0:06:12.860,0:06:13.840
we don't need to[br]worry about it,

0:06:13.840,0:06:15.280
we're not going to use[br]the same expression,

0:06:15.280,0:06:16.140
so I'm going to click

0:06:16.140,0:06:17.835
Reset in the bottom here.

0:06:17.835,0:06:20.240
So what I want[br]to do is create

0:06:20.240,0:06:22.540
the mean of the different[br]items that we have.

0:06:22.540,0:06:24.000
Sometimes if[br]you're working

0:06:24.000,0:06:26.100
with a pre-existing scale,

0:06:26.100,0:06:28.320
it might tell you to add

0:06:28.320,0:06:29.740
all the items[br]together and then

0:06:29.740,0:06:31.340
that's what represents

0:06:31.340,0:06:34.225
that theoretical concept[br]or that measure,

0:06:34.225,0:06:36.380
sometimes it might tell[br]you to use the mean.

0:06:36.380,0:06:38.600
So what I want to do[br]is compute both of

0:06:38.600,0:06:39.720
these things because they

0:06:39.720,0:06:41.295
both might be[br]helpful to me.

0:06:41.295,0:06:42.860
So what I'm going to do is

0:06:42.860,0:06:44.990
I'm going to type[br]meanofitems.

0:06:44.990,0:06:47.240
And again, that very[br]quickly lets me

0:06:47.240,0:06:48.230
differentiate between

0:06:48.230,0:06:49.970
sumofitems and[br]meanofitems.

0:06:49.970,0:06:51.700
Type & label, and again,

0:06:51.700,0:06:54.720
I'm just going to put[br]mean of items 1 through

0:06:54.720,0:07:01.905
6, click Continue.

0:07:01.905,0:07:04.900
Just like we did[br]before, click on All,

0:07:04.900,0:07:06.380
and then we're[br]going to go down

0:07:06.380,0:07:10.335
to mean, here's mean.

0:07:10.335,0:07:11.790
And when I click[br]on that, again,

0:07:11.790,0:07:14.090
it gives me that[br]sample text here.

0:07:14.090,0:07:16.975
This is very similar[br]to what we did before.

0:07:16.975,0:07:19.330
I'm going to click up, and

0:07:19.330,0:07:21.505
we're going to[br]kick over 1,

0:07:21.505,0:07:29.610
2, 3, 4, 5, and then 6.

0:07:29.610,0:07:31.070
I'm making sure to not

0:07:31.070,0:07:33.835
include this last[br]one, this sumofitems.

0:07:33.835,0:07:35.250
And then just[br]like last time,

0:07:35.250,0:07:36.150
we're going to delete out

0:07:36.150,0:07:37.280
that question mark,[br]that last comma.

0:07:37.280,0:07:38.790
We're going to[br]read through

0:07:38.790,0:07:40.505
it really quickly just[br]to avoid an error.

0:07:40.505,0:07:42.820
We've got a new[br]variable, meanofitems.

0:07:42.820,0:07:44.835
It's going to be[br]the mean of item 1,

0:07:44.835,0:07:47.265
2, 3, 4, 5, and 6.

0:07:47.265,0:07:51.130
I'm going to[br]click OK. SPSS

0:07:51.130,0:07:53.895
again showed me the[br]syntax of what it did.

0:07:53.895,0:07:55.695
I'm going to[br]minimize that.

0:07:55.695,0:07:58.080
And then here we have[br]the mean of items.

0:07:58.080,0:08:00.010
And if we really[br]quickly look at this,

0:08:00.010,0:08:01.990
I'm going to pick this[br]one, for example,

0:08:01.990,0:08:03.700
we've got 1,

0:08:03.700,0:08:06.110
1, 3, 3, 1, 2,

0:08:06.110,0:08:07.710
and a mean of 1.83 would,

0:08:07.710,0:08:09.975
just eyeballing[br]it, make sense.

0:08:09.975,0:08:11.580
If we look at this one,

0:08:11.580,0:08:13.590
3.67, 2,

0:08:13.590,0:08:15.645
3, 5, 4, 5, 3,

0:08:15.645,0:08:16.990
that would roughly[br]make sense

0:08:16.990,0:08:18.650
without having to[br]do the math of it,

0:08:18.650,0:08:21.310
but this has computed[br]the average score,

0:08:21.310,0:08:24.450
the mean score for all[br]six of those items.

0:08:24.450,0:08:26.590
So that is very[br]quickly how to

0:08:26.590,0:08:28.810
compute a new[br]variable in SPSS.

0:08:28.810,0:08:30.410
This is[br]particularly useful

0:08:30.410,0:08:32.190
when you have[br]collected data using

0:08:32.190,0:08:34.610
a pre-existing measure[br]and that measure has

0:08:34.610,0:08:36.310
instructed you to compute

0:08:36.310,0:08:38.510
the sum of items and[br]run your tests on that,

0:08:38.510,0:08:39.930
or maybe the mean of items

0:08:39.930,0:08:41.450
and run your[br]tests on that.

0:08:41.450,0:08:43.130
But this is a useful way

0:08:43.130,0:08:44.450
of understanding[br]how to create

0:08:44.450,0:08:48.190
new variables using[br]existing ones in SPSS.