14 11 18 9
Look at the following table . What type of correlation coefficient would you use to examine the relationship between ethnicity ( defined as different categories ) and political affiliation ? How about club membership ( yes or no ) and high school GPA ? Explain why you selected the answers you did .
Level of Measurement and Examples Variable X Variable Y Type of correlation Correlation being computed Nominal ( voting preference , such as Republican or Democrat ) Nominal ( gender , such as male or female ) Phi coefficient The correlation between voting preference and gender Nominal ( social class , such as high , medium , or low ) Ordinal ( rank in high school graduating class ) Rank biserial coefficient The correlation between social class and rank in high school Nominal ( family configuration , such as intact or single parent ) Interval ( grade point average ) Point biserial The correlation between family configuration and grade point average Ordinal ( height converted to rank ) Ordinal ( weight converted to rank ) Spearman rank correlation coefficient The correlation between height and weight Interval ( number of problems solved ) Interval ( age in years ) Pearson product-moment correlation coefficient The correlation between number of problems solved and the age in years
When two variables are correlated ( such as strength and running speed ), it also means that they are associated with one another . But if they are associated with one another , then why does one not cause the other ?
Given the following information , use Table B . 4 in Appendix B of Statistics for People Who ( Think They ) Hate Statistics to determine whether the correlations are significant and how you would interpret the results .
a . The correlation between speed and strength for 20 women is . 567 . Test these results at the . 01 level using a one-tailed test .
b . The correlation between the number correct on a math test and the time it takes to complete the test is . 45 . Test whether this correlation is significant for 80 children at the . 05 level of significance . Choose either a one- or a two-tailed test and justify your choice .
c . The correlation between number of friends and grade point average ( GPA ) for 50 adolescents is . 37 . Is this significant at the . 05 level for a two-tailed test ?
Use the data in Ch . 15 Data Set 3 to answer the questions below . Do this one manually or use IBM SPSS software .
a . Compute the correlation between income and level of education .