Critical Thinking and Testing Hypotheses Involving Three Variables Edward Nelson and Elizabeth Nelson California State University Fresno Sociology

Church Attendance and Opinion on Pornography Laws Previously we showed that those who attended church frequently are more likely to favor laws against the distribution of pornography to everyone regardless of age. We also observed that this does not prove that a causal relationship exists between these two variables.

Considering Other Variables That Might Affect the Relationship We know there are other variables related to church attendance and feelings about pornography. For example, women are more likely to attend church than men and also more likely to feel pornography ought to be illegal. Let’s add the variable sex into our analysis by creating two crosstabulations – (1) church attendance and sex and (2) opinions on pornography laws and sex.

Table -- Church Attendance by Sex

Table -- Pornography Laws by Sex

Interpretation Women are considerably more likely to feel that pornography ought to be illegal for everyone. Women are somewhat more likely to attend church frequently.

Adding a Third Variable (Control Variable) Perhaps the reason that those who attend church more frequently are more likely to feel that pornography ought to be illegal to everyone is that women attend church more frequently than men and women are also more likely to feel that pornography ought to be illegal for everyone. Let’s check on this possibility.

Pornography by Church Attendance--Males Only

Pornography by Church Attendance--Females Only

Interpretation If the relationship had been due to sex, then the relationship between attendance and feelings about pornography laws would have disappeared or decreased when we held sex constant. However, the relationship did not disappear. Therefore, the relationship is not due to sex. It might, of course, be due to some other variable.

Conclusion The analysis supports our hypothesis that the religious are more likely to feel that pornography ought to be illegal for everyone. This relationship is not due to sex. It is not spurious when we hold sex constant. However, it might be spurious when we hold some other variable constant. We can never prove causality. We can only make a causal connection more credible.