Hw3

read in a plain text file with variable names and assign a name to it

dta <- read.table("/Users/Tjlee/Desktop/weather/IQ_Beh.txt", header = T)

checking data

list of data

list(dta)

## [[1]]
##    Mom Dep  IQ BP
## 1    1   N 103  4
## 2    2   N 124 12
## 3    3   N 124  9
## 4    4   N 104  3
## 5    5   D  96  3
## 6    6   N  92  3
## 7    7   N 124  6
## 8    8   N  99  4
## 9    9   N  92  3
## 10  10   N 116  9
## 11  11   N  99 11
## 12  12   D  22 17
## 13  13   D  81  6
## 14  14   N 117  7
## 15  15   D 100 10
## 16  16   N  89 11
## 17  17   N 125  9
## 18  18   N 127  9
## 19  19   N 112  5
## 20  20   N  48  9
## 21  21   N 139  2
## 22  22   N 118  8
## 23  23   D 107  5
## 24  24   N 106  0
## 25  25   D 129  4
## 26  26   N 117  5
## 27  27   N 123  2
## 28  28   N 118  4
## 29  29   D  84 10
## 30  30   N 117  2
## 31  31   D 101  6
## 32  32   N 141  4
## 33  33   N 124  7
## 34  34   N 110  7
## 35  35   N  98  3
## 36  36   N 109  9
## 37  37   N 120 10
## 38  38   N 127  6
## 39  39   N 103  6
## 40  40   N 118  5
## 41  41   N 117  5
## 42  42   N 115  7
## 43  43   N 119  4
## 44  44   N 117  4
## 45  45   N  92  7
## 46  46   N 101 10
## 47  47   N 119  2
## 48  48   N 144  3
## 49  49   N 119  5
## 50  50   N 127  7
## 51  51   N 113  7
## 52  52   N 127  2
## 53  53   N 103  3
## 54  54   N 128  8
## 55  55   N  86  7
## 56  56   N 112 10
## 57  57   N 115  4
## 58  58   N 117 11
## 59  59   N  99  3
## 60  60   N 110  4
## 61  61   D 139  6
## 62  62   N 117  4
## 63  63   N  96  5
## 64  64   D 111  5
## 65  65   N 118  4
## 66  66   N 126 11
## 67  67   N 126  2
## 68  68   N  89 10
## 69  69   N 102  4
## 70  70   N 134  5
## 71  71   N  93  5
## 72  72   N 115  1
## 73  73   D  99 13
## 74  74   N  99  8
## 75  75   N 122  0
## 76  76   N 106  5
## 77  77   N 124  1
## 78  78   N 100  4
## 79  79   N 114  7
## 80  80   N 121  1
## 81  81   N 119  5
## 82  82   N 108  4
## 83  83   N 110 10
## 84  84   N 127  4
## 85  85   N 118  2
## 86  86   N 107  3
## 87  87   D 123  2
## 88  88   D 102  5
## 89  89   N 110  6
## 90  90   N 114  4
## 91  91   N 118  2
## 92  92   D 101  7
## 93  93   D 121  6
## 94  94   N 114  2

str(dta)

## 'data.frame':    94 obs. of  4 variables:
##  $ Mom: int  1 2 3 4 5 6 7 8 9 10 ...
##  $ Dep: Factor w/ 2 levels "D","N": 2 2 2 2 1 2 2 2 2 2 ...
##  $ IQ : int  103 124 124 104 96 92 124 99 92 116 ...
##  $ BP : int  4 12 9 3 3 3 6 4 3 9 ...

T-test compare two group of Depressed with IQ

t.test(IQ ~ Dep, data = dta)

## 
##  Welch Two Sample t-test
## 
## data:  IQ by Dep
## t = -1.6374, df = 15.53, p-value = 0.1216
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
##  -26.926586   3.490299
## sample estimates:
## mean in group D mean in group N 
##        101.0667        112.7848

mothers had suffered an episode of post-natal depression couldn’t influence children IQ.

P>0.05 accept Null hypothesis

t.test(BP ~ Dep, data = dta)

## 
##  Welch Two Sample t-test
## 
## data:  BP by Dep
## t = 1.4924, df = 17.14, p-value = 0.1538
## alternative hypothesis: true difference in means is not equal to 0
## 95 percent confidence interval:
##  -0.6637017  3.8788916
## sample estimates:
## mean in group D mean in group N 
##        7.000000        5.392405

mothers had suffered an episode of post-natal depression couldn’t influence children BP. P>0.05 accept Null hypothesis

#
boxplot(IQ ~ Dep, data = dta, 
        xlab = "IQ", 
        ylab = "Behavior problem score")

plot(IQ ~ BP, data = dta, pch = 10, col = dta$Dep, 
     xlab = "Behavior problem score", ylab = "IQ")
grid()

plot(BP ~ IQ, data = dta, type = "n",
     ylab = "Behavior problem score", xlab = "IQ")
text(dta$IQ, dta$BP, labels = dta$Dep, cex = 0.5)
abline(lm(BP ~ IQ, data = dta, subset = Dep == "D"))
abline(lm(BP ~ IQ, data = dta, subset = Dep == "N"), lty = 2)