Solutions HWA5
12.4:
1. H0: mu = 24,000
2. HA: mu > 24,000
3. Alpha = .05
4. x-bar_s = 24,600, z_s = (24600 – 24000)/(sigma/sqrt[n]) =(approx) 600/(4000/10) = 1.5
5. P-value = Pr(Z > z_s) = Pr(Z > 1.5) = .0668 > alpha, so retain H0.
6..
There is insufficient evidence (P-value = .0668) to conclude that
average income of 35-year-olds in
12.6:
1. H0: mu = 12.5
2. HA: mu < 12.5
3. Alpha = .05
4. x-bar_s = 9.9, z_s = (9.9 – 12.5)/(sigma/sqrt[n]) =(approx) = -2.6/(12.3/sqrt[50]) = -1.4947
5. P-value = Pr(Z < z_s) = Pr(Z < -1.4947) = .0675 > alpha, so retain H0.
6.. There is insufficient evidence (P-value = .0675) to conclude that students at this college work less than the national average of 12.5 hours per week.
12.12:
1. H0: mu = 500
2. HA: mu not = 500
3. Alpha = .05
4. x-bar_s = 477, z_s = (477 - 500)/(sigma/sqrt[n]) =(approx) = -23/(120/sqrt[91]) = -1.8284
5. P-value = Pr(|Z| > |z_s|) = 2*Pr(Z > 1.8284) = .0675 > alpha, so retain H0.
6.. There is insufficient evidence (P-value = .0675) to conclude that population mean is different from 500.