In: Statistics and Probability
1.The mode is the least used of the measures of central tendency and can only be used when dealing with nominal data. For this reason, the mode will be the best measure of central tendency (as it is the only one appropriate to use) when dealing with nominal data.
2.When the standard deviation is zero, there is no spread; that is, the all the Numbers are equal to each other.
3.Small standard deviation means less spread or the spread is concentrated.
but since range is large but it has the small standard deviation.That means the marks are concentrated over a small spread.
4.The median is the middle value in distribution when the values are arranged in ascending or descending order.
Hence,The median is less affected by outliers and skewed data than the mean, and is usually the preferred measure of central tendency when the distribution is not symmetrical.
5.most of the data are symmetric,but symmetry can be disturbed by adding some random data.
please rate my answer and comment for doubts.