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Question

What is the mean of 2, 5, 8, 14, 21?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

10

Understanding the Mean of a Dataset

The question asks us to find the mean of a given set of numbers: 2, 5, 8, 14, and 21. The mean is a measure of central tendency, often referred to as the average. It is calculated by summing all the numbers in the dataset and then dividing by the total count of numbers.

Formula for Calculating the Mean

The formula for the arithmetic mean (\(\bar{x}\)) of a set of \(n\) numbers (\(x_1, x_2, ..., x_n\)) is given by:

\[ \bar{x} = \frac{\sum_{i=1}^{n} x_i}{n} \]

Where:

  • \(\sum x_i\) represents the sum of all the numbers in the dataset.
  • \(n\) represents the total count of numbers in the dataset.

Step-by-Step Mean Calculation

Let's apply the mean formula to the given numbers: 2, 5, 8, 14, and 21.

  1. List the numbers: The given numbers are 2, 5, 8, 14, 21.
  2. Count the numbers: There are 5 numbers in the set. So, \(n = 5\).
  3. Sum the numbers: Add all the numbers together: \[ \text{Sum} = 2 + 5 + 8 + 14 + 21 \] \[ \text{Sum} = 7 + 8 + 14 + 21 \] \[ \text{Sum} = 15 + 14 + 21 \] \[ \text{Sum} = 29 + 21 \] \[ \text{Sum} = 50 \] The sum of the numbers is 50.
  4. Calculate the mean: Divide the sum by the count of numbers: \[ \text{Mean} = \frac{\text{Sum}}{\text{Count}} = \frac{50}{5} \] \[ \text{Mean} = 10 \]

Therefore, the mean of the numbers 2, 5, 8, 14, and 21 is 10.

Comparing with Options

Let's check the calculated mean against the provided options:

  • Option 1: 10
  • Option 2: 9
  • Option 3: 8.5
  • Option 4: 9.5

Our calculated mean is 10, which matches Option 1.

Number Value
First 2
Second 5
Third 8
Fourth 14
Fifth 21
Total Sum 50
Count (n) 5
Mean (Sum/n) 10

Revision Table: Key Statistical Measures

Measure Description Calculation Method
Mean (Average) Sum of all values divided by the number of values. Sum / Count
Median The middle value in a dataset when arranged in ascending or descending order. If there's an even number of values, it's the average of the two middle values. Order data, find middle value(s)
Mode The value that appears most frequently in the dataset. A dataset can have one mode (unimodal), multiple modes (multimodal), or no mode. Identify most frequent value(s)
Range The difference between the highest and lowest values in a dataset. Highest value - Lowest value

Additional Information: Measures of Central Tendency

The mean, median, and mode are the three most common measures of central tendency. They each provide a different way to describe the "center" or typical value of a dataset. The mean is sensitive to extreme values (outliers), while the median is less affected by them. The mode is useful for identifying the most common category or value, particularly in non-numeric data.

In this specific problem, we were asked to find the mean, which represents the arithmetic average of the numbers.

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Similar Questions

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Important Questions from Elementary Statistics

  1. In a colony 5 families have 1 child, 7 families have 2 children, 8 families have 3 children and 3 families have 4 children.What is the mode of the number of children.

  2. What will be the difference between mean and median of the given data?

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    B. 3 and 5

    C. 5 and 4

    D. 3 and 4

  4. For which set of numbers do the mean, median and mode all have the same value?

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