In a class, the mean weight of 4 students is 90 kg and standard deviation is 30, then 95% confidence interval would be accordingly:: (A) 60-80, (B) 30-150, (C) 60-120, (D) 70-110
Answer is B. Here, Mean = 90 ; Standard deviation = 30
95% confidence interval = Mean +/- 2 S.D
Hence, 90+ (2x30) = 90+60 = 150
             90- (2x30) = 90-60 = 30