we will not get same sample size as previous study. Previous study used the prevalence of a study which was done earlier. Sample size will be different
we will not get same sample size as previous study. Previous study used the prevalence of a study which was done earlier. Sample size will be different
Sample size (n’)= za2 x SD2 / Precision2 Where precision2 = za2 x SD2 / previous sample size (n) i.e. n’=za2 x SD2 / (za2 x SD2/ n) n’=n Isnt this the same!?
this formula is used when the study measures a continuous outcome. Prevalence or incidence of the condition is not given in the previous research which is published.
The formula shows the minimum sample size. If you have finite population (when the total number of people in the sampling frame from which the samples are selected are less )- please use correction formula for finite population
If you get the standard deviation of knowledge scores value and sample size from a previous similar published research -- you can calculate precision value 👍
the scenario that is described in this video - is a study to estimate the value of mean (sd) of the outcome variable. Purpose of a case control study involving 2 means (for cases and controls) - will be to test the hypothesis. Hypothesis will be that there is no difference between the mean values among cases and controls
Using that precision formula we will get the same sample size of the previous study so what's the use of that
we will not get same sample size as previous study. Previous study used the prevalence of a study which was done earlier. Sample size will be different
we will not get same sample size as previous study. Previous study used the prevalence of a study which was done earlier. Sample size will be different
Thank you very much Sir, you did great job!!!
you are most welcome
thank you so much for very valuable information.
Glad it was helpful!
Sample size (n’)= za2 x SD2 / Precision2
Where precision2 = za2 x SD2 / previous sample size (n)
i.e.
n’=za2 x SD2 / (za2 x SD2/ n)
n’=n
Isnt this the same!?
Precision is = Z alpha * standard error of mean
standard error of mean = standard deviation / square root of n
Sorry I didn't mention those steps. But it's still the same, isn't it?
Yes it will be same 😊
Sir, is this a Prevalence or Incidence or Longitudinal problem?
this formula is used when the study measures a continuous outcome. Prevalence or incidence of the condition is not given in the previous research which is published.
I wanna known wheather the formula does we used the same formula if the question requires the minimum of sample size?
The formula shows the minimum sample size. If you have finite population (when the total number of people in the sampling frame from which the samples are selected are less )- please use correction formula for finite population
Can I use the first precision formula to calculate Sample Size for assessing knowledge of 500 ASHA
If you get the standard deviation of knowledge scores value and sample size from a previous similar published research -- you can calculate precision value 👍
Can I use the first formula for the known, finite population ??
yes sure
@@PublicHealthResearchDrSandheep Thank you so much
Which sd is to be considered pre test or post test
anticipated difference in mean values and sd of difference in means (in case of pre and post test comparisons)
Sir please share me the source you used for this particular formula
Cochran,WG (1977). Sampling Techniques (3rd edition.). Wiley.
hello sir.. what if we have two mean and SD that is for case and control in previous study
the scenario that is described in this video - is a study to estimate the value of mean (sd) of the outcome variable. Purpose of a case control study involving 2 means (for cases and controls) - will be to test the hypothesis. Hypothesis will be that there is no difference between the mean values among cases and controls
For case control study involving 2 means and sd, you can calculate the sample size using the formula for comparing the difference between means
@@PublicHealthResearchDrSandheep Respected sir can u upload an example video on comparing the diferrence between means
It seems there is a circulation in your formula.
Can you please clarify
if the study is new how i can calculate
you can assume the proportion in a logical way … or you can assume that the prevalence is 50%
@@PublicHealthResearchDrSandheep Thank you
pleas shear me the source you used
pubmed.ncbi.nlm.nih.gov/24049221/
Where is the sample size calculation for SD?
It is sample size calculation based on SD value from previous research 🙏👍