Question

x represents number of girls among 10 children. Use range rule of thumb to determine whether 1 girl in 10 births is significantly low. Give maximum and minimum

Answer 1

The range rule of thumb tells that the range is generally about four times the standard

deviation.

$\mu = E(X) = \sum xP(x)$

$E(X) = 0\times 0.003+1 \times 0.016+2 \times 0.036+--------+10 \times 0.024 = 5.104$

Standard Deviation = 1.769

The Range Rule of Thumb says that the range is about four times the standard deviation.

$R = 4 \sigma$

Maximum value $= \mu + 2\sigma = 5.104+2 \times 1.769 = 8.642$

Minimum value $= \mu-2 \sigma = 5.10-2 \times 1.769 = 1.566$