How to interpret the results of the linear regression test in SPSS?

By Riya Jain & Priya Chetty on September 24, 2019

The previous article explained how to interpret the results obtained in the correlation test. Case analysis was demonstrated, which included a dependent variable (crime rate) and independent variables (education, implementation of penalties, confidence in the police, and the promotion of illegal activities). The aim of that case was to check how the independent variables impact the dependent variables. The test found the presence of a correlation, with the most significant independent variables being education and the promotion of illegal activities. Now, the next step is to perform a regression test.

However, this article does not explain how to perform the regression test, since it is already present here. This article explains how to interpret the results of a linear regression test on SPSS.

What is regression?

Regression is a statistical technique to formulate the model and analyze the relationship between the dependent and independent variables. It aims to check the degree of relationship between two or more variables. This is done with the help of hypothesis testing. Suppose the hypothesis needs to be tested for determining the impact of the availability of education on the crime rate. Then the hypothesis framed for the analysis would be:

  • Null hypothesis H01: Availability of education does not impact the crime rate.
  • Alternate hypothesis HA1: Availability of education impacts the crime rate.
  • Null hypothesis H02: Promotion of illegal activities does not impact the crime rate.
  • Alternate hypothesis HA1: Promotion of illegal activities impacts the crime rate.
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Then, after running the linear regression test, 4 main tables will emerge in SPSS:

  1. Variable table
  2. Model summary
  3. ANOVA
  4. Coefficients of regression

Variable table

The first table in SPSS for regression results is shown below. It specifies the variables entered or removed from the model based on the method used for variable selection.

  1. Enter
  2. Remove
  3. Stepwise
  4. Backward Elimination
  5. Forward Selection

Variables Entered/ Removeda

ModelVariables EnteredVariables RemovedMethodModel
1 Availability of Education, Promotion of Illegal Activitiesb   Enter 1
a. Dependent Variable: Crime Rate
b. All requested variables entered. 

There is no need to mention or interpret this table anywhere in the analysis. It is generally unimportant since we already know the variables.

Model summary

The second table generated in a linear regression test in SPSS is Model Summary. It provides detail about the characteristics of the model. In the present case, promotion of illegal activities, crime rate and education were the main variables considered. The model summary table looks like below.

Model summary

ModelRR-squareAdjusted R-squareStd. Error of the Estimate
1.713a.509 .501 .60301
a. Predictors: (Constant), Availability of Education, Promotion of Illegal Activities

Elements of this table relevant for interpreting the results:

  • R-value represents the correlation between the dependent and independent variable. A value greater than 0.4 is taken for further analysis. In this case, the value is .713, which is good.
  • R-square shows the total variation for the dependent variable that could be explained by the independent variables. A value greater than 0.5 shows that the model is effective enough to determine the relationship. In this case, the value is .509, which is good.
  •  Adjusted R-square shows the generalization of the results i.e. the variation of the sample results from the population in multiple regression. It is required to have a difference between R-square and Adjusted R-square minimum. In this case, the value is .501, which is not far off from .509, so it is good.

Therefore, the model summary table is satisfactory to proceed with the next step. However, if the values were unsatisfactory, then there is a need for adjusting the data until the desired results are obtained.

ANOVA table

This is the third table in a regression test in SPSS. It determines whether the model is significant enough to determine the outcome. It looks like below.

ANOVAa

Model Sum of Squares df Mean Square F Sig.
1 Regression 97.860 2 24.465 67.283 .000b
  Residual 94.540 262 .364    
  Total 192.400 264      
a. Dependent Variable: Crime Rate
Predictors: (Constant), Availability of Education, Promotion of Illegal Activities

Elements of this table relevant for interpreting the results are:

  • P-value/ Sig value: Generally, 95% confidence interval or 5% level of the significance level is chosen for the study. Thus the p-value should be less than 0.05. In the above table, it is .000. Therefore, the result is significant.
  • F-ratio: It represents an improvement in the prediction of the variable by fitting the model after considering the inaccuracy present in the model. A value is greater than 1 for F-ratio yield efficient model. In the above table, the value is 67.2, which is good.

These results estimate that as the p-value of the ANOVA table is below the tolerable significance level, thus there is a possibility of rejecting the null hypothesis in further analysis.

Coefficient table

Below table shows the strength of the relationship i.e. the significance of the variable in the model and magnitude with which it impacts the dependent variable. This analysis helps in performing the hypothesis testing for a study.

Coefficientsa

Unstandardized CoefficientsStandardized Coefficients
Model B Std. Error Beta t Sig.
1 (Constant) .486 .148 3.278.001
  Availability of Education -.178 .105-.1981.705.089
  Promotion of Illegal Activities .464.084 .441 5.552 .000

Only one value is important in interpretation: Sig. value. The value should be below the tolerable level of significance for the study i.e. below 0.05 for 95% confidence interval in this study. Based on the significant value the null hypothesis is rejected or not rejected.

If Sig. is < 0.05, the null hypothesis is rejected. If Sig. is > 0.05, then the null hypothesis is not rejected. If a null hypothesis is rejected, it means there is an impact. However, if a null hypothesis is not rejected, it means there is no impact.

In this case, the interpretation will be as follows.

Coefficients table

Independent Variable Sig value Hypothesis Testing Result at 95% confidence interval Interpretation
Availability of Education 0.089 Null Hypothesis not rejected (0.089 > 0.05) No significant change in crime rate due to the availability of Education. This is because of the Sig. value is 0.08, which is more than the acceptable limit of 0.05.
Promotion of Illegal Activities 0.000 Null Hypothesis Rejected (0.000 < 0.05) The significant change in crime rate due to the promotion of illegal activities, because of the Sig. value is 0.000, which is less than the acceptable value of 0.05. With a 1% increase in the promotion of illegal activities, the crime rate will increase by 0.464% (B value).

Therefore, the analysis suggests that the promotion of illegal activities has a significant positive relationship with the crime rate.

Lastly, the findings must always be supported by secondary studies that have found similar patterns.

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Priya is the co-founder and Managing Partner of Project Guru, a research and analytics firm based in Gurgaon. She is responsible for the human resource planning and operations functions. Her expertise in analytics has been used in a number of service-based industries like education and financial services.

Her foundational educational is from St. Xaviers High School (Mumbai). She also holds MBA degree in Marketing and Finance from the Indian Institute of Planning and Management, Delhi (2008).

Some of the notable projects she has worked on include:

  • Using systems thinking to improve sustainability in operations: A study carried out in Malaysia in partnership with Universiti Kuala Lumpur.
  • Assessing customer satisfaction with in-house doctors of Jiva Ayurveda (a project executed for the company)
  • Predicting the potential impact of green hydrogen microgirds (A project executed for the Government of South Africa)

She is a key contributor to the in-house research platform Knowledge Tank.

She currently holds over 300 citations from her contributions to the platform.

She has also been a guest speaker at various institutes such as JIMS (Delhi), BPIT (Delhi), and SVU (Tirupati).

 

I am a master's in Economics from Amity University. Having a keen interest in Econometrics and data analysis, I was a part of the Innovation Project of Daulat Ram College, Delhi University. My core expertise and interest are in environment-related issues. Apart from academics, I love music and exploring new places.

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