lab 10

lab10.R

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+library(mosaicData)
+library(MASS)
+
+# Q1
+set.seed(123)
+
+truemean=mean(TenMileRace$net)
+
+lowerbounds=rep(0, 20)
+upperbounds=rep(0, 20)
+containsmean=rep(FALSE, 20)
+
+for(i in 1:20)
+{
+  racetimes25=TenMileRace$net[sample(1:nrow(TenMileRace), 25)]
+  
+  raceci=t.test(racetimes25)
+  
+  lowerbounds[i]=raceci$conf.int[1]
+  upperbounds[i]=raceci$conf.int[2]
+  containsmean[i]=truemean >= lowerbounds[i] & truemean <= upperbounds[i]
+}
+
+ciresults=data.frame(
+  sample=1:20,
+  lower=lowerbounds,
+  upper=upperbounds,
+  containstruemean=containsmean
+)
+
+ciresults
+sum(containsmean)
+
+# Q2
+femalecats=subset(cats, Sex=="F")
+malecats=subset(cats, Sex=="M")
+
+femalebodyci=t.test(femalecats$Bwt)
+femaleheartci=t.test(femalecats$Hwt)
+malebodyci=t.test(malecats$Bwt)
+maleheartci=t.test(malecats$Hwt)
+
+femalebodyci
+femaleheartci
+malebodyci
+maleheartci
+
+# Q3
+set.seed(123)
+
+racetimes30=TenMileRace$net[sample(1:nrow(TenMileRace), 30)]
+racetimes230=TenMileRace$net[sample(1:nrow(TenMileRace), 230)]
+racetimes430=TenMileRace$net[sample(1:nrow(TenMileRace), 430)]
+
+ci30=t.test(racetimes30)
+ci230=t.test(racetimes230)
+ci430=t.test(racetimes430)
+
+ci30
+ci230
+ci430
+
+ci30$conf.int
+ci230$conf.int
+ci430$conf.int
+
+# Q4
+confidence=function(data, conflevel)
+{
+  ci=t.test(data, conf.level=conflevel)
+  
+  lowerbound=ci$conf.int[1]
+  upperbound=ci$conf.int[2]
+  confpercent=attr(ci$conf.int, "conf.level") * 100
+  
+  cat("We are", confpercent, 
+      "percent sure that the mean is between", 
+      lowerbound, "and", upperbound, ".")
+}
+
+confidence(survey$Age, 0.99)
+
+# Q5
+confidence=function(data, conflevel, meaninfo, units)
+{
+  CI=t.test(data, conf.level=conflevel)
+  
+  lowerbound=CI$conf.int[1]
+  upperbound=CI$conf.int[2]
+  confpercent=attr(CI$conf.int, "conf.level") * 100
+  
+  cat("We are", confpercent, "percent sure that the mean", 
+      meaninfo, "is between", lowerbound, "and", upperbound, 
+      units, ".")
+}
+
+confidence(survey$Age, 0.99, "student age", "years")
+
+# Q6
+confidence=function(data, conflevel=0.95, meaninfo, units)
+{
+  CI=t.test(data, conf.level=conflevel)
+  
+  lowerbound=CI$conf.int[1]
+  upperbound=CI$conf.int[2]
+  confpercent=attr(CI$conf.int, "conf.level") * 100
+  
+  cat("We are", confpercent, "percent sure that the mean", 
+      meaninfo, "is between", lowerbound, "and", upperbound, 
+      units, ".")
+}
+
+confidence(survey$Age, 0.90, "student age", "years")
+confidence(survey$Age, 0.95, "student age", "years")
+confidence(survey$Age, quantity="student age", units="years")