<<"HypothesisTesting`"

data={18,12,18,13,13,16,11,17,20,14,15,14,16,15,15,17,13,14,16,13}
n=Length[data]
σ=1.5
priemer=Mean[data]
μ0=20
T=((priemer-μ0)/σ)(Sqrt[n])
α=0.05
kvantil2=Quantile[NormalDistribution[0,1],(1-(α/2))]
If[Abs[T]<kvantil2,Print["nezamietam Ho"],Print["zamietam Ho"]]

kvantil1=Quantile[NormalDistribution[0,1],(1-α)]
If[T>-kvantil1,Print["nezamietam Ho"],Print["zamietam Ho"]]

s=StandardDeviation[data]
T=N[((priemer-μ0)/s)(Sqrt[n])]

Tkvantil=Quantile[StudentTDistribution[n-1],(1-(α/2))]