T-test



R codes for various

Statistical tests

A) T-test

ex9-37

> Indoor=scan("clipboard")

Read 33 items

> Outdoor=scan("clipboard")

Read 33 items

> Indoor

[1] 0.07 0.08 0.09 0.12 0.12 0.12 0.13 0.14 0.15 0.15 0.17 0.17 0.18 0.18 0.18

[16] 0.18 0.19 0.20 0.22 0.22 0.23 0.23 0.25 0.26 0.28 0.28 0.29 0.34 0.39 0.40

[31] 0.45 0.54 0.62

> Outdoor

[1] 0.29 0.09 0.47 0.54 0.97 0.35 0.49 0.84 0.86 0.28 0.32 0.32 1.55 0.66 0.29

[16] 0.21 1.02 1.59 0.90 0.52 0.12 0.54 0.88 0.49 1.24 0.48 0.27 0.37 1.26 0.70

[31] 0.76 0.99 0.36

> t.test(Indoor,Outdoor,paired=T)

Paired t-test

data: Indoor and Outdoor

t = -5.9509, df = 32, p-value = 1.251e-06

alternative hypothesis: true difference in means is not equal to 0

95 percent confidence interval:

-0.5450513 -0.2670700

sample estimates:

mean of the differences

-0.4060606

B) Analysis of Variance: ANOVA, F-test

exp10-1

> y=scan("clipboard")

Read 24 items

> x=scan("clipboard")

Read 24 items

> y

[1] 656 788 734 721 679 699 789 773 787 686 732 775 737 639 696 672 717 727 535

[20] 629 542 559 587 520

> x

[1] 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4

> x=as.factor(x)

> x

[1] 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 4 4 4 4 4 4

Levels: 1 2 3 4

> summary(aov(y~x))

Df Sum Sq Mean Sq F value Pr(>F)

x 3 127385 42462 25.125 5.474e-07 ***

Residuals 20 33801 1690

---

Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

>

C) Simple Linear Regression Analysis

ex12-37

> x=scan("clipboard")

Read 10 items

> y=scan("clipboard")

Read 10 items

> plot(x,y)

> summary(lm(y~x))

Call:

lm(formula = y ~ x)

Residuals:

Min 1Q Median 3Q Max

-0.209799 -0.045309 -0.001910 0.082312 0.142137

Coefficients:

Estimate Std. Error t value Pr(>|t|)

(Intercept) 2.1416477 0.0767926 27.89 2.95e-09 ***

x 0.0068006 0.0002618 25.98 5.17e-09 ***

---

Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Residual standard error: 0.1101 on 8 degrees of freedom

Multiple R-Squared: 0.9883, Adjusted R-squared: 0.9868

F-statistic: 675 on 1 and 8 DF, p-value: 5.172e-09

> abline(2.1416,.0068)

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