In a population of pregnant female, Hb is estimated on 100 women with standard detion of 1gm %. The standard error is:: (A) 1, (B) 0.1, (C) 0.01, (D) 10
Answer is B. The most common parameters of interest in health are mean (m) and propoion (p). They tend to vary from sample to sample, if we take repeated samples from a target population the sample means and propoion will have a gaussian or non-gaussian distribution, called sampling distribution. The sample means will tend to vary around a population standard detion, but this variability is now called standard error of mean (SEM). Similarly we can get a standard error of propoion. The larger the standard error, larger will be the variability and less is our confidence in the sample results. SE (mean) = Sample standard detion where 'n' = sample size [?]n SE (propoion) = [?]p(1-p) where 'p' = propoion, and 'n'= sample size [?]n In this question, we can apply the given information to the formula for calculation of Standard error of mean as: 1/10= 0.1(Square root of 100 is 10) Ref: Park's Textbook of Preventive and Social Medicine; 18th edition; Page-649