Shortcut Trick
Arrange the given 12 numbers in ascending order: 12, 25, 25, 42, 45, 45, 54, 58, 59, 60, 65, 87.
Since the total number of terms (N = 12) is even, the median is the average of the two middle terms (6th and 7th terms).
The 6th term is 45 and the 7th term is 54.
Median = (45 + 54) ÷ 2 = 49.5.
∴ The correct answer is 49.5.
Alternate Method
Given:
Data set: 42, 45, 58, 87, 45, 54, 65, 12, 25, 25, 59, 60
Total number of observations (N) = 12
Formula Used:
When the total number of observations (N) is even:
Median = [(N/2)th term + (N/2 + 1)th term] ÷ 2
Calculations:
⇒ First, arrange the given data set in ascending order:
12, 25, 25, 42, 45, 45, 54, 58, 59, 60, 65, 87
⇒ Here, the total number of terms N = 12, which is even.
⇒ The 6th term (N/2) = 45
⇒ The 7th term (N/2 + 1) = 54
⇒ Median = (6th term + 7th term) ÷ 2
⇒ Median = (45 + 54) ÷ 2
⇒ Median = 99 ÷ 2 = 49.5
⇒ Thus, the median of the given data set is 49.5.
⇒ Option (1) is correct because the calculated median is 49.5.
⇒ Option (2) is incorrect because 59.5 does not represent the average of the two middle terms.
⇒ Option (3) is incorrect because 54 is only the 7th term, not the average of the two middle terms.
⇒ Option (4) is incorrect because 45 is only the 6th term, not the average of the two middle terms.
∴ The correct answer is 49.5.
Additional Information
Median for Odd Number of Terms
If the total number of observations (N) is odd, the median is the middlemost term, which is the ((N + 1)/2)th term after arranging the data in ascending or descending order.
Mean (Arithmetic Average)
Mean is the sum of all observations divided by the total number of observations: Mean = (Sum of all terms) ÷ N.
Mode
Mode is the value that appears most frequently in a data set. A data set can have one mode, more than one mode, or no mode at all.
Empirical Relationship
For a moderately skewed distribution, the relationship between mean, median, and mode is: Mode = 3 × Median − 2 × Mean.