SaiBook.us Statistics

Example

Title: Mean for grouped data

Grade: 9-a Lesson: S1-L4

Explanation: The best way to understand statistics is by looking at some examples. Take turns and read each example for easy understanding.

Examples:

Find out the mean for the given observations

$1$

Step 1a

Mid-points of class-interval and add frequencies

Explanation: Now take the midpoints of the class interval.

i.e, \$(2+4)/2 = 3,(4+6)/2 = 5,(6+8)/2 = 7\$.

Add all the frequencies

i.e, \$6 + 5 + 9 = 20\$.

Step 1b

Multiplying frequency with midpoints

Explanation: Multiply the midpoint values with frequency

i.e, \$3×6 = 18,5×5 = 25,7×9 = 63\$

Sum of midpoint values

i.e, \$18+25+63 = 106\$

Step 1c

Mean = \$(\sumx_i f_i) / (\sumf_i)\$

Explanation: \$\sumx_i f_i = 106\$,

\$\sumf_i = 20\$

Mean = \$106/20 = 5.3\$