The sum of 100 observations and the sum of their squares are 400 and 2475, respectively. Later on, three observations, 3, 4 and 5, were found to be incorrect. If the incorrect observations are omitted, then the variance of the remaining observations is:
100 प्रेक्षणों (Observation) का योग और उनके वर्गों का योग क्रमशः 400 और 2475 है। बाद में पता चला कि तीन प्रेक्षण 3, 4 और 5 गलत थे। यदि गलत प्रेक्षणों को हटा दिया जाए, तो शेष प्रेक्षणों का प्रसरण (Variance) है:
Answer और ExplanationAnswer and explanation
Answer: (A) 9
शेष 97 प्रेक्षण (Observations): Σx = 400 − (3 + 4 + 5) = 388
Σx² = 2475 − (9 + 16 + 25) = 2425
माध्य (Mean) = 38897 = 4
प्रसरण (Variance) = Σx²n − (माध्य)² = 242597 − 16 = 25 − 16 = 9
✓
प्रसरण 9 है।
Remaining 97 observations: Σx = 400 − (3 + 4 + 5) = 388
Σx² = 2475 − (9 + 16 + 25) = 2425
Mean = 38897 = 4
Variance = Σx²n − (mean)² = 242597 − 16 = 25 − 16 = 9
✓
The variance is 9.
Source: RRB S.C · 12 Feb 2026। Solution: Prashant Sir, Vijayastra।Source: RRB S.C · 12 Feb 2026. Solution by Prashant Sir, from Vijayastra.