If the bih weight of each of the 10 babies born in a hospital in a day is found to be 2.8 kg, then the Standard detion of this sample will be:-

**Core Concept**
The standard deviation (SD) is a measure of the amount of variation or dispersion of a set of values. In this case, we are dealing with a sample of 10 babies' birth weights, and we want to calculate the standard deviation of this sample.

**Why the Correct Answer is Right**
To calculate the standard deviation, we first need to calculate the variance. The formula for the sample variance is the sum of the squared differences between each data point and the mean, divided by the number of data points minus one (n-1). In this case, the mean is 2.8 kg, and we have 10 data points. However, since all the babies have the same birth weight, the variance will be zero, and the standard deviation will also be zero. This is because there is no variation in the data.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not take into account the fact that all the babies have the same birth weight, which results in a variance and standard deviation of zero.
* **Option B:** This option is incorrect because it assumes that the standard deviation can be calculated without considering the variation in the data.
* **Option C:** This option is incorrect because it does not provide a valid formula for calculating the standard deviation.

**Clinical Pearl / High-Yield Fact**
When dealing with a sample of data where all the values are the same, the standard deviation will always be zero. This is an important concept to remember when working with statistical analysis in medicine.

**Correct Answer: D. 0**