Part A 1. A study compared oral diversity between croplands and wetlands. Independent random samples of 120 cropland regions and 61 wetland regions were obtained in the Southern Great Plains. The cropland regions contained an average of 15.03 native oral species, with a standard deviation of 4.83; the wetland regions had an average of 16.76 and a standard deviation of 4.95. STAT 15] Assignment 5 Total: 97 marks [a] Test if the mean number of native oral species is lower in cropland regions. Use the 1% significance level. [8 marks] [b] Obtain a two-sided 99% condence interval for the difference in mean number of oral species between cropland and wetland regions. [4 marks] 4. A plumbing company is interested in whether the reasons for service calls tend to differ between weekdays and weekends. The following table summarizes a random sample of 4m} service calls. giving both the reason why the call was made and whether or not it was the weekend; do the data provide evidence of an association between the two variables? Test at the 5% significance level. (8 marks) STAT 15] Assignment 5 Totol: 5'? marks \"n mm n Installation 1211] 135 M