A simple random sample of size n=36 is obtained from a population that is skewed right with μ=80 and σ=24.(a) Describe the sampling distribution of xˉ.(b) What is P(x>86.8) ?(c) What is P(x≤70.2) ?(d) What is P(74<xˉ<89.6) ?
Q. A simple random sample of size n=36 is obtained from a population that is skewed right with μ=80 and σ=24.(a) Describe the sampling distribution of xˉ.(b) What is P(x>86.8) ?(c) What is P(x≤70.2) ?(d) What is P(74<xˉ<89.6) ?
Identify Distribution: Identify the distribution of the sample mean xˉ for a large sample size from a skewed population.Since n=36 is sufficiently large, by the Central Limit Theorem, xˉ is approximately normally distributed with mean μ=80 and standard deviation σ/n=24/36=4.
Calculate P(xˉ>86.8): Calculate P(xˉ>86.8) using the standard normal distribution.Convert xˉ>86.8 to a Z-score: Z=486.8−80=1.7.Using standard normal tables or calculator, P(Z>1.7)≈0.0446.
Calculate P(xˉ≤70.2): Calculate P(xˉ≤70.2) using the standard normal distribution.Convert xˉ≤70.2 to a Z-score: Z=470.2−80=−2.45.Using standard normal tables or calculator, P(Z≤−2.45)≈0.0071.
Calculate P(74<xˉ<89.6): Calculate P(74<xˉ<89.6) using the standard normal distribution.Convert to Z-scores: Z1=474−80=−1.5 and Z2=489.6−80=2.4.Using standard normal tables or calculator, P(−1.5<Z<2.4)≈P(Z<2.4)−P(Z<−1.5)≈0.9918−0.0668=0.925.