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How you can learn Standard deviation almost instantly-Class 11 Mathematics

Updated: Jul 6, 2023

standard deviation cover page

The complete guide to understanding mean deviation and standard deviation.

Standard deviation is a commonly used term in Statistics. It has applications in Mathematics and Economics as well. This blog gives you a basic idea of Mean Deviation and Standard Deviation and how to calculate these.

I am a math educator having taught Mathematics for three decades both at the high school and college level. So here's showing you how incredibly easy and scoring this topic is. My students ace this topic because it is so incredibly easy and question on this topic are pretty direct.

So, let's start the magical journey of learning!

Mean Deviation:

Keep in mind that mean deviation and standard deviation are two ways of measuring the dispersion of data. Mean Deviation basically gives you how far the data is distributed from the mean or median. So, in Mean Deviation problems, you need to calculate two types, mean deviation about the mean and mean deviation about the median.

Again, there are two types of problems. Firstly, we have a set of discrete observations . These are easier to calculate.

mean deviation basic formula

Then we have a frequency distribution which may be grouped or ungrouped. For problems of these type, you will use the formula and evaluate. Formulas are given in the images.

This topic is fairly easy and my students usually get it right provided they remember the correct formula. Mean deviation is not a very reliable method of measuring the deviation. Hence we have the standard deviation which is a more reliable and widely used method to evaluate the dispersion.

mean deviation for a frequency distribution

Standard deviation

The mean of the squared deviations is called the variance and standard deviation is the square root of the variance. You calculate the standard deviation for a set of discrete values and for a frequency distribution. The formula for calculating the standard deviation for a set of discrete values is quite simple.

basic standard deviation formulas

For calculating the standard deviation for a frequency distribution with equal class intervals, you can use three methods. First, you have the direct method. If the values are large, you have two methods to calculate the standard deviation, namely, the Shortcut method or the Deviation method and the Step Deviation method.

Note that these two methods are more or less similar, with a slight difference. As I tell my students, you are free to use any formula of your choice in the exams. But keep in mind, that if a particular question demands the use of a particular method, then you have to abide by the question.

How Online Tutoring helps!

I have given you a brief gist on how you should go about preparing Mean Deviation and Standard Deviation. If you still need some help or guidance, you can contact me for online tutoring. You would require around three sessions of an hour each to understand this topic.

You could choose between one to one tutoring or group tutoring. You can message me on to register.

To make math education universally accessible and affordable, you can join me for a webinar on this topic. This webinar may run over three days. Minimum number of participants is ten.

You can message me for payment details and registration. I hope a great many students will be benefited by this webinar.

Would you care to spread this blog and upcoming webinar to students who may just need that little extra help? If so, kindly share this blog with other students.

Hope, you have learnt how to go about studying mean deviation and standard deviation. You can visit

here for more free resources.

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Let me know if you have any more queries.

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