Consider the following two scenarios: 1. the mean height of coastal redwood trees is known to be 200 feet. in order to test whether a community of coastal trees were growing to be healthy in a park with high rates of tourism, a random sample of 20 trees were measured. it was found that for the 20 sampled trees, the average height was 197.5 feet with a standard deviation of 6.7. it is known that tree heights follow a normal distribution. 2. the mean height of coastal redwood trees is known to be 200 feet. in order to test whether a community of coastal trees were growing to be healthy in a park with high rates of tourism, a random sample of 20 trees were measured. it was found that for the 20 sampled trees, the average height was 197.5 feet. it is known that tree heights follow a normal distribution with a standard deviation of 7. which of the following is correct: a. in the second scenario, the population standard deviation is not known, therefore a z-test should be used. b. in the second scenario, the sample standard deviation is known, therefore a z- test should be used. c. in the second scenario, the population standard deviation is known, thereforea t-test should be used. d. in the second scenario, the population standard deviation is known, therefore a z-test should be used.