18. The ages of all the patients in the isolation ward of the hospital are 38, 26. 13, 41 and 22. What is the population variance? A) 106.8 B) 91.4 C) 240.3 D) 42.4 19. The weights (in grams) of the contents of several small bottles are 4. 2. 5. 4. 5, 2 and 6. What is the sample variance? A) 6.92 B) 4.80 C) 1.96 D) 2.33 20. What is the relationship between the variance and the standard deviation? A) Variance is the square root of the standard deviation B) Variance is the square of the standard deviation C) Variance is twice the standard deviation D) No constant relationship between the variance and the standard deviation 21. What is the median of 26. 30. 24, 32. 32. 31, 27 and 29? A) 32 B) 29 C) 30 D) 29.5 22. The mean of all possible sample means is equal to the A) population variance. B) o' . C) sample variance. D) population mean. 23. A statewide sample survey is to be made. First, the state is subdivided into counties. Seven counties are selected at random and further sampling is concentrated on these seven counties. What type of sampling is this? A) Simple random B) Nonproportional C) Cluster D) Stratified