A simple random sample of 25 filtered 100 mm cigarettes is obtained and the tar content of each cigarette is measured. The sample has a mean of 15 mg and a standard deviation of 4 mg. Use a 0.05 significance level to test the claim that the mean tar content of filtered 100 mm cigarettes is less than 20 mg, what is the value of test statistic? 1. z = 6.25 2. z = -6.25 3. t = 6.25 4. t = -6.25