an insurance company, based on past experience, estimates the mean damage for a natural disaster in its area is $5,000. after introducing several plans to prevent loss, it randomly samples 200 policyholders and finds the mean amount per claim was $4,800 with a standard deviation of $1,300. does it appear the prevention plans were effective in reducing the mean amount of a claim? use the 0.05 significance level. a. what is the decision rule? (negative amount should be indicated by a minus sign. round your answer to 3 decimal places.)