Answer: To estimate the number of families to be interviewed, we can use the formula for sample size calculation in a survey.
The formula for sample size calculation is:
n = (Z * σ / E)^2
Where:
n = required sample size
Z = Z-score corresponding to the desired confidence level (95% confidence level corresponds to Z = 1.96)
σ = standard deviation of the sample
E = desired margin of error (estimate to be within Tk. 1500)
Given information:
Pilot sample size (n) = 12
Standard deviation of the sample (σ) = Tk. 24000
Desired margin of error (E) = Tk. 1500
Substituting the values into the formula:
n = (1.96 * 24000 / 1500)^2
Calculating this:
n ≈ 31.86^2
n ≈ 1014.12
Therefore, the estimated number of families to be interviewed is approximately 1014.
Keep in mind that this is an estimate and rounding up to the nearest whole number, the recommended sample size would be 1015 families.