Follow the instructions below to generate odds ratios:
Click File > New > Syntax on the main menu, as shown below:
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You will be presented with the IBM SPSS Statistics Statistics Syntax Editor window, as shown below:
Published with written permission from SPSS Statistics, IBM Corporation.
Make sure that you are working with the correct dataset. You can do this by confirming that the name in brackets after the plum.sav file name in the IBM SPSS Statistics Statistics Data Editor window is the same as selected for the Active: option in the IBM SPSS Statistics Statistics Syntax Editor window, as highlighted below:
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Note: Although the name of the dataset above is "DataSet2", yours might be called something different. This is OK so long as they are the same.
To calculate the odds ratios and their 95% confidence intervals in the new file, copy the following highlighted syntax into the Syntax Editor verbatim:
Published with written permission from SPSS Statistics, IBM Corporation.
Explanation: This last stage calculates the odds ratios and their 95% confidence intervals from the parameter estimates and stores these values in new variables within the 'plum' file. To make life simpler, you can copy and paste the following code for this last part:
COMPUTE Exp_B = EXP(Estimate).
COMPUTE Lower = EXP(LowerBound).
COMPUTE Upper = EXP(UpperBound).
FORMATS Exp_B Lower Upper (F8.3).
EXECUTE.
Click Run > All on the main menu to generate the output, as shown below:
Published with written permission from SPSS Statistics, IBM Corporation.
You will have added some extra columns into your file that represent the odds ratio and its 95% confidence intervals, as highlighted below:
Published with written permission from SPSS Statistics, IBM Corporation.
Having run all five steps of the SPSS Statistics procedures, you should now have all the information you need to start interpreting the results from your ordinal regression.
SPSS Statistics will generate quite a few tables of output when carrying out ordinal regression analysis. Below we briefly explain the main steps that you will need to follow to interpret your ordinal regression results. If you want to be taken through all these sections step-by-step, together with the relevant SPSS Statistics output, we do this in our enhanced ordinal regression guide. You can learn more about our enhanced content here. First, take a look through these steps:
The odds of business owners considering tax to be too high was 1.944 (95% CI, 1.101 to 3.431) times that of non-business owners, a statistically significant effect, Wald χ^{2}(1) = 5.255, p = .022.
An increase in age (expressed in years) was associated with an increase in the odds of considering tax too high, with an odds ratio of 1.274 (95% CI, 1.196 to 1.357), Wald χ^{2}(1) = 56.355, p < .001.
If you are unsure how to interpret your ordinal regression results, check the assumptions of an ordinal regression or conduct the additional SPSS Statistics procedures required to analyse your data, we show you how to do this in our enhanced ordinal regression guide. We also show you how to write up the results from your assumptions tests and ordinal regression output if you need to report this in a dissertation/thesis, assignment or research report. We do this using the Harvard and APA styles. You can learn more about our enhanced content here.