**Core Concept**
The median is the middle value in a dataset when it is ordered from smallest to largest. Understanding the concept of median and its relation to probability is essential in statistics and population studies.

**Why the Correct Answer is Right**
The probability of a value being above the median is 50% because, by definition, the median splits the dataset into two equal parts: one part with values below the median and the other part with values above the median. This is true for any dataset, regardless of its distribution or shape. In a perfectly symmetrical distribution, the probability of a value being above the median is 0.5, as half of the values fall above the median.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the probability of a value being above the median is not dependent on the sample size or the spread of the data. The median remains the middle value, dividing the data into equal parts.

**Option B:** This option is incorrect because the probability of a value being above the median is not influenced by the mean or the mode of the dataset. The median is a measure of central tendency that is independent of the other measures.

**Option C:** This option is incorrect because the probability of a value being above the median is not affected by the skewness of the distribution. The median remains the middle value, regardless of the skewness.

**Clinical Pearl / High-Yield Fact**
Remember that the median is a robust measure of central tendency that is less affected by outliers compared to the mean. This makes the median a useful statistic in medical research and clinical studies where data may be skewed or contain outliers.

**Correct Answer: D. 50%**