Final answer:
The standard deviation is used together with the mean to measure the spread of data values in a dataset. In a symmetrical distribution, the mean, median, and mode are all equal. To find deviations and patterns in the data set, we first calculate the mean followed by the standard deviation. The correct option is D.
Step-by-step explanation:
The standard deviation is used in conjunction with the mean. Standard deviation is a measure of how much the values in a dataset deviate from the mean. It is a statistical tool that allows us to understand the spread of data points in a data set, by quantifying the average of the squared differences from the mean. When using the standard deviation, we are assuming that the data is centered around the mean.
In a symmetrical distribution, the mean, median, and mode are all equal and located at the center of the distribution. To compute the standard deviation for a given data set (for example, 10; 11; 15; 15; 17; 22), we would first calculate the mean and then use the sample formula for standard deviation. Once we have the standard deviation, we could also determine what number is two standard deviations above the mean.