Question

Difficulty: MediumBasic Tools of Economic Analysis

The table below shows the distribution of weekly cassava output (in bags) produced by a sample of farmers in a agricultural cooperative:

Output (Bags)Number of Farmers (ff)
10−1410 - 1422
15−1915 - 1955
20−2420 - 2488
25−2925 - 2955

What is the mean weekly output of cassava per farmer?

  1. A
    19.0 bags19.0\text{ bags}
  2. B
    19.5 bags19.5\text{ bags}
  3. 21.0 bags21.0\text{ bags}Answer
  4. D
    23.0 bags23.0\text{ bags}

Answer

The mean weekly output of cassava per farmer is 21.0 bags21.0\text{ bags}.
The correct output of 21.0 bags21.0\text{ bags} is derived by determining the midpoint of each class interval (12,17,22,2712, 17, 22, 27), multiplying each by its respective number of farmers, summing these products to get 420 bags420\text{ bags}, and dividing by the total number of farmers (2020).

Step-by-Step Solution

1
Calculate the class midpoint (xx) for each class interval.
Midpoints are: 10+142=12\frac{10+14}{2} = 12, 15+192=17\frac{15+19}{2} = 17, 20+242=22\frac{20+24}{2} = 22, and 25+292=27\frac{25+29}{2} = 27.
For grouped data, the midpoint represents the central value of each class interval.
2
Multiply each midpoint (xx) by its corresponding frequency (ff) to obtain f×xf \times x.
2×12=242 \times 12 = 24, 5×17=855 \times 17 = 85, 8×22=1768 \times 22 = 176, 5×27=1355 \times 27 = 135.
This determines the estimated total output within each interval.
3
Calculate the sum of frequencies (∑f\sum f) and the sum of products (∑fx\sum fx).
∑f=2+5+8+5=20\sum f = 2 + 5 + 8 + 5 = 20; ∑fx=24+85+176+135=420\sum fx = 24 + 85 + 176 + 135 = 420.
These totals are needed to apply the grouped mean formula.
4
Divide ∑fx\sum fx by ∑f\sum f to compute the arithmetic mean (xˉ\bar{x}).
xˉ=42020=21.0 bags\bar{x} = \frac{420}{20} = 21.0\text{ bags}.
The formula for the mean of grouped frequency distribution is xˉ=∑fx∑f\bar{x} = \frac{\sum fx}{\sum f}.

Key Concept

Arithmetic Mean of Grouped Data
Estimated Time:1m 30s
Rate this question