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 400 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) 3 STAT 151 Assignment 5 Total: 97 marks Weekend Reason for Call No Yes Total Estimation 44 11 55 Repair 130 60 190 Installation 120 15 135 Other 16 4 20 Total 310 90 400Part A 1. A study compared floral 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 floral species, with a standard deviation of 4.83; the wetland regions had an average of 16.76 and a standard deviation of 4.95. 1 STAT 151 Assignment 5 Total: 97 marks (a) Test if the mean number of native floral species is lower in cropland regions. Use the 1% significance level. (8 marks) (b) Obtain a two-sided 99% confidence interval for the difference in mean number of floral species between cropland and wetland regions. (4 marks)