Shortcut Trick
Mode is the observation that occurs most frequently in a data set.
Count the frequency of each observation:
⇒ 27 appears 2 times.
⇒ All other numbers (23, 38, 42, 45, 58, 69, 71) appear only 1 time.
Since 27 has the highest frequency, the mode is 27.
∴ The correct answer is 27.
Alternate Method
Given:
Observations: 23, 27, 38, 42, 27, 58, 69, 71, 45
Formula Used:
Mode = Observation with the maximum frequency
Calculations:
Let us arrange the given data in ascending order to easily count the frequencies:
⇒ Arranged Data: 23, 27, 27, 38, 42, 45, 58, 69, 71
Now, let us construct a frequency table for the observations:
⇒ Frequency of 23 = 1
⇒ Frequency of 27 = 2
⇒ Frequency of 38 = 1
⇒ Frequency of 42 = 1
⇒ Frequency of 45 = 1
⇒ Frequency of 58 = 1
⇒ Frequency of 69 = 1
⇒ Frequency of 71 = 1
Since the observation 27 occurs the maximum number of times (frequency = 2), it is the mode of the given data set.
Let us analyze why the other options are incorrect:
⇒ Option (1) 71 is incorrect because its frequency is only 1.
⇒ Option (3) 45 is incorrect because its frequency is only 1.
⇒ Option (4) 42 is incorrect because its frequency is only 1.
∴ The correct answer is 27.
Additional Information
Definition of Mode
The mode is the value that appears most frequently in a data set. A data set can have one mode (unimodal), two modes (bimodal), multiple modes (multimodal), or no mode at all if all values occur with equal frequency.
Empirical Relationship between Mean, Median, and Mode
For a moderately skewed distribution, the relationship is given by: Mode = 3 × Median − 2 × Mean.
Mean and Median
Mean is the average of all observations (Sum ÷ Total count). Median is the middlemost value when the data is arranged in ascending or descending order.