Soru

Zorluk: OrtaMeasures of Central Tendency

The table below shows the frequency distribution of prices (in ₦) for tubers of yam sold in an agricultural market:

Price (₦)Frequency (ff)
10 – 143
15 – 195
20 – 247
25 – 293
30 – 342

What is the mean price of a tuber of yam?

  1. A
    ₦19
  2. ₦21Cevap
  3. C
    ₦22
  4. D
    ��23

Cevap

The mean price of a tuber of yam is ₦21.
The mean price is calculated by multiplying each class interval midpoint by its frequency, adding these products together to obtain 420, and dividing by the total number of observations (20), giving ₦21.

Adım Adım Çözüm

1
Determine the midpoint (xx) for each price class interval.
Class 10–14: x=12x = 12; Class 15–19: x=17x = 17; Class 20–24: x=22x = 22; Class 25–29: x=27x = 27; Class 30–34: x=32x = 32.
Midpoints represent the central value of grouped class intervals.
2
Multiply each midpoint (xx) by its corresponding frequency (ff) to find fxfx, and sum all products (fx\sum fx).
fx=(12×3)+(17×5)+(22×7)+(27×3)+(32×2)=36+85+154+81+64=420\sum fx = (12 \times 3) + (17 \times 5) + (22 \times 7) + (27 \times 3) + (32 \times 2) = 36 + 85 + 154 + 81 + 64 = 420.
Weighting midpoints by frequency gives the total aggregate value.
3
Sum the total frequencies (f\sum f) and calculate the mean (xˉ=fxf\bar{x} = \frac{\sum fx}{\sum f}).
f=3+5+7+3+2=20\sum f = 3 + 5 + 7 + 3 + 2 = 20. Therefore, xˉ=42020=21\bar{x} = \frac{420}{20} = 21.
The grouped mean is total aggregate value divided by total number of items.

Anahtar Kavram

Calculation of the Arithmetic Mean from Grouped Frequency Data
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