# NCERT Class 11-Math՚s: Exemplar Chapter – 15 Statistics Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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**Question 13**:

Mean and standard deviation of items are and , respectively. Find the sum of all the item and the sum of the squares of the items.

**Answer**:

**Question 14**:

If for a distribution and the total number of item is , find the mean and standard deviation.

**Answer**:

**Question 15**:

Find the mean and variance of the frequency distribution given below:

**Answer**:

## Long Answer Type

**Question 16**:

Calculate the mean deviation about the mean for the following frequency distribution:

Class Interval | |||||

Frequency |

**Answer**:

Given: the frequency distribution

To find: the mean deviation about the mean

Let us make a table of the given data and append other columns after calculations

Class Interval | Mid Value | Frequency | |

Total |

Here mean,

So the above table with more columns is as shown below,

Class Interval | Mid Value | Frequency | |||

Total |

Hence Mean Deviation becomes,

Therefore, the mean deviation about the mean of the distribution is

**Question 17**:

Calculate the mean deviation from the median of the following data:

Class Interval | |||||

Frequency |

**Answer**:

Given: the frequency distribution

To find: the mean deviation from the median

Let us make a table of the given data and append other columns after calculations

Class Interval | Mid Value | Frequency | Cumulative Frequency (c. f) |

Total |

Now, here , which is even.

Here median class term,

This observation lie in the class interval , so median can be written as,

Here , , and , substituting these values, the above equation becomes,

So the above table with more columns is as shown below,

Class Interval | Mid Value | Frequency | ||

Total |

Hence Mean Deviation becomes,

Therefore, the mean deviation about the median of the distribution is 7