SPSS 10:  Data entry and t-tests

1.  Decide on variables for the data set
 Look at the data set.  What information do you have about each subject?  Those pieces of information will be your variables.  In a simple experiment, you will know what level of the Independent Variable the person experienced, you will assign a Subject Number (to make it easy to track the data), you will have the subject’s scores on each Dependent Variable.  You will need to name each and know the possible values and what the values mean.

In this week’s problem set:
 IV:  Level of processing
  1 = rhymes
  2 = semantic
 Subject Number
1-15 for each level of the IV
 Average Reaction Time
  In milliseconds
 Number of Correct Answers
  0-20 possible

Need short names for each variable.  LOP, SUBJECT, REACT, CORRECT

2. Open SPSS
 SPSS 10 comes up in DATA VIEW with a empty data file.

3. Label Variables
 Click on the VARIABLE VIEW tab in lower left of data file.  This changes what you see.  You can now give SPSS information about your variables.

a. Do variable 1 first.  Click in the box in the “Name” column, on the row “1”.  Type the name of your variable “LOP”.  Tab.  SPSS goes to default for variable type (number).  You can click on the 3 … next to number to see the options for variable type.  Tab over to “Label” and give SPSS information on what LOP means (Type “levels of processing”). Tab to “Values” and give SPSS information regarding what 1 and 2 will mean by clicking on the 3 …  In the dialogue box, type “1” for value, hit the tab key, then type “rhyme” for the value label, then hit the “Add” button.  In the same dialogue box, type “2” for value, hit the tab key, then type “semantic” for the value label, then hit the “Add” button.  Hit the “OK” button.  You are done with variable 1.

b. Do variable 2.  Click in the box in the “Name” column, on the row “2”.  Type the name of your variable “SUBJECT”.  Tab.  Tab over to “Label” and give SPSS information on what SUBJECT means (Type “subject number”). You do not need to give SPSS any other information about this variable, since it has no meaningful labels.

c. Do variable 3.  Click in the box in the “Name” column, on the row “3”.  Type the name of your variable “REACT”.  Tab.  Tab over to “Label” and give SPSS information on what REACT means (Type “average reaction time”). You do not need to give SPSS any other information about this variable, since it has no meaningful labels.

d. Do variable 4.  Click in the box in the “Name” column, on the row “4”.  Type the name of your variable “CORRECT”.  Tab.  Tab over to “Label” and give SPSS information on what CORRECT means (Type “number of correct responses”). You do not need to give SPSS any other information about this variable, since it has no meaningful labels.
 

4.  Data Entry

a. Click on the “Data View” tab in the lower left hand corner.

b. You should see variables names at the top of columns.

c. Place cursor in “lop” column for row 1.

d. Type 1, for level 1 of LOP, hit tab key.  This moves you to next column.

e. Type in 1, for subject 1 of LOP level 1.  Hit tab.

f. Type in reaction time score (575).  Hit tab.

g. Type in correct answers (14).  Hit tab.

h. THIS SHOULD MOVE YOU TO ROW 2.

i. Continue through the data set.

5.  Save Data
 Every now and then you should save the data to your disk.  How frequently depends on your data entry speed and willingness to redo data entry.  Computers crash.  Most often they do this if it has been a while since you last saved the data.  Usually they crash right before you intend to save the next set of data.  The computer ate my homework is never an excuse in this class.

6.  Computing a between-subjects t-test

a. Analyze Menu pull down to the “Compare Means” option, which opens a sub-menu.  Select “Independent-Samples t-test” from this menu.

b. A dialogue box opens that will let you tell SPSS your IV and DVs.

c. Click once on LOP, then hit the “>” key next to “Grouping Variable” (grouping is more general term for independent variable).

d. Click on the “Define Groups” key.  Type in the values for your two groups.  Group 1 is 1 and Group 2 is 2.  Click continue.  The box in Grouping Variable should now read “lop(1 2)”.

e. Click once on reaction time, then hit the “>” key next to “Test Variable” (test variable is SPSS’s term for dependent variable).

f. Click once on correct answers, then hit the “>” key nextto “Test Variable” (test variable is SPSS’s term for dependent variable).

g. Click the “OK” button.
 

7.  You now have an output that provides basic descriptive statistics and the results of a t-test for each dependent variable.
 

8.  Print that out!