0
$\begingroup$

I have some syntax for SPSS and it produces everything that I need perfectly, although for some reason it spits it out one tailed instead of two tailed. Is there any way of editing this syntax so that it uses a two tailed analyses?

REGRESSION
/DESCRIPTIVES MEAN STDDEV CORR SIG N
/MISSING LISTWISE
/STATISTICS COEFF OUTS CI(95) R ANOVA CHANGE ZPP
/CRITERIA=PIN(.05) POUT(.10)
/NOORIGIN
/DEPENDENT SumF1
/METHOD=ENTER Gender
/METHOD=ENTER Age
/METHOD=ENTER HighSchool UnderGrad PostGrad
/METHOD=ENTER Student BlueCollar WhiteCollar
/METHOD=ENTER Single Married DeFacto
/SCATTERPLOT=(*ZPRED ,*ZRESID)
/RESIDUALS HISTOGRAM(ZRESID) NORMPROB(ZRESID).
$\endgroup$
1
  • $\begingroup$ It would be helpful if you describe your variables, what do they mean, and also name the output table in which you find one-tailed tests instead of two-tailed what you expected. $\endgroup$
    – ttnphns
    Commented Nov 22, 2011 at 13:01

2 Answers 2

1
$\begingroup$

Surprisingly you can not specify this for the output. Are you sure yours is displaying the one-tailed test? The example below (and this is using version 19) is displaying the two-tailed test as the default for me.

data list free / v1 v2.
begin data
1 10
2 12
3 14
4 19
end data.

REGRESSION
  /MISSING LISTWISE
  /STATISTICS COEFF OUTS R ANOVA
  /CRITERIA=PIN(.05) POUT(.10)
  /NOORIGIN 
  /DEPENDENT v1
  /METHOD=ENTER v2.

This produces the table of coefficient estimates below; enter image description here

So I have two degrees of freedom for the t-test (since I estimated two parameters, v2 and the intercept), and an estimate of 5.581. Looking at the t-test table on wikipedia you can see a t-value of 5.581 for a two-tailed test would produce a p-value somewhere in between .02 and .05 (that table is slightly odd compared to most t-tables, and 100 minus the percentage produces the p-value of interest). You should also notice from that table that the p-value's associated with one-tailed tests are simply the p-value of the two-tailed test divided by two. So even though SPSS does not give the option to change whether you use a one tailed or two tailed test, it is fairly trivial to do do the calculation yourself. (A more exact two-tailed p-value from this online calculator suggests it is .0306, which is rounded up in the table below)

So if you wanted to go from the two-tailed test to the one-tailed test, you would just divide the p-value by 2. Conversely if you wanted to go from a one-tailed test to a two-tailed test, you would just multiple the p-value by 2.

$\endgroup$
0
$\begingroup$

There are no one-tailed tests on coefficients from Regression except, of course, that an F test is always one tailed.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.