For Mrs Rekha, probability of having a baby of BW < 2500 gms is 0.50 and of having a BW 2500-2999 gms is 0.20. So the probability for Mrs. Rekha to have a baby of BW < 3 kg is
## **Core Concept**
The problem involves calculating the probability of a baby having a birth weight (BW) of less than 3 kg, given the probabilities of having a baby with a BW less than 2500 gms and having a BW between 2500-2999 gms. This requires understanding basic probability theory and how to combine probabilities of mutually exclusive events.
## **Why the Correct Answer is Right**
To find the probability that Mrs. Rekha will have a baby with a BW < 3 kg, we need to consider the probabilities of two mutually exclusive events: having a baby with a BW < 2500 gms and having a baby with a BW between 2500-2999 gms. The probability of having a baby with a BW < 2500 gms is given as 0.50, and the probability of having a baby with a BW between 2500-2999 gms is 0.20. Since these events are mutually exclusive (a baby can't have two different weights at the same time), we add the probabilities of these two events to find the total probability of having a baby with a BW < 3 kg. Therefore, the calculation is 0.50 + 0.20 = 0.70.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it suggests a calculation or probability that does not match the information provided or the correct calculation.
- **Option B:** This option is incorrect because, like Option A, it does not align with the correct calculation of probabilities for the given events.
- **Option D:** This option is incorrect because it does not represent the correct sum of the probabilities for having a baby with a BW < 2500 gms and a BW between 2500-2999 gms.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that when dealing with probabilities of mutually exclusive events, the probabilities are added to find the total probability of either event occurring. In the context of fetal growth and birth weight, understanding the distribution of birth weights and the factors influencing them is crucial. A birth weight of less than 3 kg can be a significant factor in neonatal care and outcomes.
## **Correct Answer:** . 0.7