<prompt> S.D. is 1.96 the confidence limit is -63.6066.609599  <response>: Ans. is c i.e., 95 For 1.96 SD 2 SD, confidence limit is 95. Area under standard normal distribution curve o It can be understand by the 68-95-99.7 rule - i The area between one standard detion on either side of the mean - 1 a will include 68 percent of the values. ii The area between two standard detions on either side of the mean will cover 95 of values. iii The area between three standard detion will include 99.7 of values. o These limits on either side of the mean is called confidence limits. o For example, if we are considering the 95 percent confidence limits Area under 2 SD, that means that 95 of the values in the distribution will be included between the limits 2 SD -- x - 2 a. Therefore, the probability of a reading falling outside confidence limit 95 is only 5, i.e. 1 in 20 P 0.05. o So, For 1 SD, confidence limit 68 For 2 SD, confidence limit 95 For 3 SD, confidence limit -- 99.7 Note: Generally we consider that for 2SD, confidence limit is 95. However, actual exact values are slightly different-o Actual parameters in a Normal Gaussian distribution. o Mean - 1 SD la limits include 68.27 values o Mean - 2SD 26 limits include 95.45 values o Mean - 1.96SD 1.966 limits include 95 values o Mean - 3SD 3a limits include 99.73 values o Mean - 2.58SD - 2.58 a limits include 99 values Also know: o Values that differ from the mean by more than 2SD are rare, being only 4.55. o Values higher or lower than the Mean - 3SD 36 are very rare, being only 0.27. o 6 SD 3 on either side of mean cover almost the entire range of a variable character SD divides the range into 6 equal sub-range o Minimum sample size required for establishment of normal range for any health parameter: 300 healthy subjects. o Confidence limits of normal curve can never be 100. therefore the limbs of curve never touch base line. 