Find the mean and variance for the data
${x_i}$
$92$
$93$
$97$
$98$
$102$
$104$
$109$
${f_i}$
$3$
$2$
$3$
$2$
$6$
$3$
$3$
Find the mean and variance for the data
| ${x_i}$ | $92$ | $93$ | $97$ | $98$ | $102$ | $104$ | $109$ |
| ${f_i}$ | $3$ | $2$ | $3$ | $2$ | $6$ | $3$ | $3$ |
The data is obtained in tabular form as follows.
| ${x_i}$ | ${f_i}$ | ${f_i}{x_i}$ | ${{x_i} - \bar x}$ | ${\left( {{x_i} - \bar x} \right)^2}$ | ${f_i}{\left( {{x_i} - \bar x} \right)^2}$ |
| $92$ | $3$ | $276$ | $-8$ | $64$ | $192$ |
| $93$ | $2$ | $186$ | $-7$ | $49$ | $98$ |
| $97$ | $3$ | $291$ | $-3$ | $9$ | $27$ |
| $98$ | $2$ | $196$ | $-2$ | $4$ | $8$ |
| $102$ | $6$ | $612$ | $2$ | $4$ | $24$ |
| $104$ | $3$ | $312$ | $4$ | $16$ | $48$ |
| $109$ | $3$ | $327$ | $9$ | $81$ | $243$ |
| $22$ | $2200$ | $640$ |
Here, $N = 22,\sum\limits_{i = 1}^7 {{f_i}{x_i}} = 2200$
$\therefore \bar x = \frac{1}{n}\sum\limits_{i = 1}^7 {{f_i}{x_i}} = \frac{1}{{22}} \times 2200 = 100$
Variance $\left( {{\sigma ^2}} \right) = \frac{1}{N}\sum\limits_{i = 1}^7 {{f_i}{{\left( {{x_i} - \bar x} \right)}^2} = } \frac{1}{{22}} \times 640 = 29.09$
Similar Questions
Find the mean and variance for the following frequency distribution.
Classes
$0-30$
$30-60$
$60-90$
$90-120$
$120-150$
$50-180$
$180-210$
$f_i$
$2$
$3$
$5$
$10$
$3$
$5$
$2$
Find the mean and variance for the following frequency distribution.
| Classes | $0-30$ | $30-60$ | $60-90$ | $90-120$ | $120-150$ | $50-180$ | $180-210$ |
| $f_i$ | $2$ | $3$ | $5$ | $10$ | $3$ | $5$ | $2$ |
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