All Exams Test series for 1 year @ ₹349 only
Question

The mean and standard deviation of 100 terms are 50 and 3, respectively. The sum of squares of the 100 terms is:

The correct answer is
2,50,900

This problem requires us to find the sum of squares of 100 terms, given their mean and standard deviation. We will use the relationship between mean, standard deviation, and the sum of squares.

Understanding the Given Information

  • Number of terms, n = 100
  • Mean of the terms, $\bar{x}$ = 50
  • Standard deviation of the terms, $\sigma$ = 3

Relevant Statistical Formulas

The formula for the mean ($\bar{x}$) is given by:

$$ \bar{x} = \frac{\sum x}{n} $$

The formula for the variance ($\sigma^2$) is given by:

$$ \sigma^2 = \frac{\sum x^2}{n} - (\bar{x})^2 $$

From this variance formula, we can rearrange it to solve for the sum of squares ($\sum x^2$):

$$ \frac{\sum x^2}{n} = \sigma^2 + (\bar{x})^2 $$ $$ \sum x^2 = n \left( \sigma^2 + (\bar{x})^2 \right) $$

Step-by-Step Calculation

  1. Calculate the variance: Since the standard deviation ($\sigma$) is 3, the variance ($\sigma^2$) is $3^2$. $$ \sigma^2 = 3^2 = 9 $$
  2. Calculate the square of the mean: The mean ($\bar{x}$) is 50, so the square of the mean is $50^2$. $$ (\bar{x})^2 = 50^2 = 2500 $$
  3. Calculate the sum of squares ($\sum x^2$): Using the rearranged variance formula: $$ \sum x^2 = n \left( \sigma^2 + (\bar{x})^2 \right) $$ Substitute the values we have: n = 100, $\sigma^2$ = 9, and $(\bar{x})^2$ = 2500. $$ \sum x^2 = 100 (9 + 2500) $$ $$ \sum x^2 = 100 (2509) $$ $$ \sum x^2 = 250900 $$

Conclusion

The sum of squares of the 100 terms is 2,50,900.

Was this answer helpful?

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

Need Expert Advice?

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App