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Question

Calculate the standard deviation for the following data.
$3, 4, 5, 6, 7$

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$\sqrt{2}$

To calculate the standard deviation for the dataset \(3, 4, 5, 6, 7\), we will follow these steps:

  1. Calculate the mean (\(\bar{x}\)) of the data. 
    \(\bar{x} = \frac{3 + 4 + 5 + 6 + 7}{5} = \frac{25}{5} = 5\)
  2. Find the deviations of each data point from the mean and square each deviation.
    • \(3 - 5 = -2\quad \rightarrow \quad (-2)^2 = 4\)
    • \(4 - 5 = -1\quad \rightarrow \quad (-1)^2 = 1\)
    • \(5 - 5 = 0\quad \rightarrow \quad (0)^2 = 0\)
    • \(6 - 5 = 1\quad \rightarrow \quad (1)^2 = 1\)
    • \(7 - 5 = 2\quad \rightarrow \quad (2)^2 = 4\)
  3. Calculate the average of these squared deviations. 
    \(\frac{4 + 1 + 0 + 1 + 4}{5} = \frac{10}{5} = 2\)
  4. The standard deviation (\(\sigma\)) is the square root of the variance. 
    \(\sigma = \sqrt{2}\)

Therefore, the standard deviation of the given dataset is \(\sqrt{2}\), which matches the correct answer option provided.

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Similar Questions

  1. The standard deviation of 12 values is 3. If each value is increased by 4, then find the variance of the new set of values.
  2. Calculate the standard deviation for the following data. 

    4, 7, 9, 10, 15

  3. If the variance of 5 values is 0.64, then what will be its standard deviation?

Important Questions from Standard Deviation

  1. Calculate the mean from the following table.

    Scores

    Frequencies

    0-10

    2

    10-20

    4

    20-30

    12

    30-40

    21

    40-50

    6

    50-60

    3

    60-70

    2

  2. Find the standard deviation of the following data (rounded off to two decimal places).

    5, 3, 4, 7

  3. If the standard deviation of a population is 5, what will be its variance?

    A. 10

    B. 15

    C. 25

    D. 12.5

  4. The variance of a set of data is 196. Then the standard deviation of the data is.

    A. ± 14

    B. 14

    C. 96

    D. 98
  5. The variance of a set of data is 144. Then the standard deviation of the data is:

    A. ±12

    B. 12

    C. 44

    D. 72

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