True or false 2. The variation in sample means is measured by the standard deviation 3. The margin of error for a sample is dependent on a known or estimated population standard deviation 4. The margin of error can be reduced by increasing the size of the sample 5. A one-tailed test can occur when the null hypothesis assumes the true pollution mean is greater than or equal to some value or less than OR equal to some value 6. The level of confidence and level of significance must always add up to 100% 7. Type II errors are always preferred to Type | errors 8. Experimental studies allow for researchers to control some factors of the situation 9. A regression cannot under any circumstances prove causality 10. In a simple regression with one independent variable the coefficient of determination is equal to the correlation coefficient squared 11. In a simple regression with one independent variable the error term is assumed to have the same variance for all values of the independent variable 12. A multiple regression may have multiple dependent variables 13. In a regression estimation the residual can be observed, but the error term cannot be observed 14. The number of independent variables in a multiple regression can be greater than the number of observations