Question

The average age of public jeepneys playing in Metro Manila is 15 years. Assume that the standard deviation is 4 years. If a random sample of 64 public jeepneys is chosen, find the probability that the mean of jeepneys ages is Between 12 to 19 years

Answer 1

$$P(12<X<19)=P(Z<\dfrac{19-15}{4/\sqrt{64}})$$

$$-P(Z\le\dfrac{12-15}{4/\sqrt{64}})$$

$$=P(Z<8)-P(Z\le-6 )$$

$$\approx 1-0=1$$