In a comparison of countries, those having economies less dependent on oil wealth will be more democratic than will countries having economies more dependent on oil wealth. Consider the following data, which present information for 20 countries with non-oil-dependent economies and fifteen countries with oil-dependent economies. The dependent variable is a 7-point level-of-democracy scale, with higher scores denoting more democracy. Oil-dependent economy Mean Democracy Standard Error
No 4.7 0.51
Yes 2.6 0.28

Required:
a. State the null hypothesis for the non-oil-dependent/oil-dependent comparison.
b. Calculate the difference between the means of the democracy scale for the two groups of countries. Calculate the standard error of the difference. Calculate the t-statistic. What is the p-value using a two-tailed test?
c. Suppose we have strong theoretical reasons for a one-tailed test. Is the difference statistically significant? Explain how you know.
d. Based on the results in parts B and C, suppose a researcher decides to reject the null hypothesis. Is this decision supported by the statistical evidence? Explain.