Statistics
Mean Deviation About Mean
nta_pyq_2024_jan
Grade 11
Question:
Let the median and the mean deviation about the median of 7 observations $170,125,230,190,210,a,b$ be $170$ and $\dfrac{205}{7}$ respectively. Then the mean deviation about the mean of these 7 observations is:
Step-by-Step Solution
Key Concept: Median $=170$ (4th value when sorted). Mean deviation about median $=\frac{1}{7}\sum|x_i-170|=205/7$. Use this to find $a+b=300$. Then mean $=175$. Compute mean deviation about mean.
$a+b=300$, $\bar{x}=175$. MD about mean $=30$.
Correct Answer: 3