The first quartile of a list of values is the median of the lower half of the values.​

Correct Answer

c. The median of the lower half of the values
This matches the standard statistical definition, where data is ordered from lowest to highest, split at the median (Q2), and Q1 is found as the middle value of the bottom half.​

Option Analysis

• a. Half the mean of the values: Incorrect, as the mean measures central tendency by averaging all values, and halving it has no relation to quartiles, which divide ordered data positionally.​

• b. One standard deviation below the mean of the values: Incorrect, since standard deviation quantifies spread around the mean, not positional divisions like quartiles.​

• c. The median of the lower half of the values: Correct, as confirmed across definitions; for even counts, it may average two values in that half.​

• d. None of the above: Incorrect, since option c precisely defines Q1.​

The first quartile definition statistics refers to Q1, the value below which 25% of ordered data falls, serving as a key measure of distribution in descriptive statistics.​

Calculation Method

Order the dataset ascendingly, find the median (Q2) to split halves, then compute Q1 as the median of the lower half. For n values, locate at position (n+1)/4; average adjacent if non-integer.​
Example: Dataset. Median is 5; lower half; Q1=2.​

Why It Matters

First quartile helps detect skewness, outliers, and spread via box plots, essential for CSIR NET Life Sciences data interpretation.​
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