Correct Answer - Option 2 : 2.57
Concept:
To find the mean deviation, use the following steps
Step 1: Find the mean value for the given data values
Step 2: Now, subtract mean value form each of the data value given (Note: Ignore the minus symbol)
Step 3: Now, find the mean of those values obtained in step 2.
Mean deviation \(\rm = \dfrac {1}{n} \sum |x - \bar x|\)
Calculations:
Given data is 2, 9, 9, 3, 6, 9, 4
⇒ n = 7
Mean \(\rm \bar x = \dfrac {2+9+9+3+6+9+4}{7}\)
⇒ \(\rm \bar x = 6\)
Mean deviation \(\rm = \dfrac {1}{n} \sum |x - \bar x|\)
⇒ Mean deviation \(\rm = \dfrac {1}{7} {(|2-6|+|9-6|+|9-6|+|3-6|+ \|6-6|+|9-6+|4-6|)}\)
⇒ Mean deviation = 2.57
Hence, the mean deviation of the data 2, 9, 9, 3, 6, 9, 4 is 2.57