What is the justification for using either a right-or left-tailed test. Question 7 options: If as a researcher, you suspect that the Mean of your group will increase, compared to the population, then you will use a right-tailed test. If, as a researcher, you suspect that that the Mean of your group will decrease, use a left-tailed test. If the Mean of your group decreases compare to the population Mean, one uses a left-tailed test and if the Mean of your group increases compared to the population, use a right-tailed test. The decision to use either a right or left-tailed test is dependent on whether or not prior research, usually a literature review, indicates whether or not the Mean of your group will either increase or decrease