Consider the following dataset: 9, 12, 15, 18, 21. What is the standard deviation of this dataset?a.3.6b.4c.4.24d.5.5

To calculate the standard deviation of a dataset, you need to follow these steps:

1. Find the mean of the dataset by adding up all the numbers and dividing by the total count. In this case, the sum of the numbers is 9 + 12 + 15 + 18 + 21 = 75. Since there are 5 numbers in the dataset, the mean is 75/5 = 15.

2. Subtract the mean from each number in the dataset and square the result. For example, for the first number (9), the result is (9 - 15)^2 = 36. Repeat this step for all the numbers in the dataset.

3. Find the mean of the squared differences calculated in step 2. Add up all the squared differences and divide by the total count. In this case, the sum of the squared differences is (36 + 9 + 0 + 9 + 36) = 90. Since there are 5 numbers in the dataset, the mean of the squared differences is 90/5 = 18.

4. Take the square root of the mean of the squared differences calculated in step 3. In this case, the square root of 18 is approximately 4.24.

Therefore, the standard deviation of the dataset 9, 12, 15, 18, 21 is approximately 4.24.

So, the correct answer is c. 4.24.