Following are the ages (in years) of 6 people in a group: 25, 30, 35, 40, 45 and 50. What is the standard deviation of their ages (rounded to two decimal places)?

Question

Question

This question was previously asked in

RRB NTPC Graduate Level CBT-I Official Paper (Held On: 06 Jun, 2025 Shift 3)

Answer 1

Given:

Ages of the group: 25, 30, 35, 40, 45, 50

n = 6

Formula used:

Standard Deviation (σ) =

Where:

n = number of data points

= mean of the data points

= each data point

Calculation:

Step 1: Calculate the mean:

⇒

Step 2: Calculate the squared differences from the mean:

for each data point:

For 25:

For 30:

For 35:

For 40:

For 45:

For 50:

Step 3: Calculate the variance:

Variance =

⇒ Variance =

Step 4: Calculate the standard deviation:

σ =

⇒ σ = 8.54

∴ The correct answer is option (1).

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