Please use R program in order to find the confidence interval 8.39 Some research

Question

Please use R program in order to find the confidence interval

8.39 Some researchers have conjectured that stem-pitting disease in peach tree seedlings might be related to the presence or absence of nematodes in the soil. Hence, weed and soil treatment using herbicides might be effective in promoting seedling growth. Researchers conducted an experiment to compare peach tree seedling growth with soil and weeds using with one of three treatments: A: Control (no herbicide) B: Herbicide with Nemagone C: Herbicide without Nemagone

Explanation / Answer

Result:

Groups: A=1, B=2, C=3

Rcode:

x1<-c(66,67,74,73,75,64,85,84,76,82,79,86,91,93,88,87,90,86)

grp<-c(1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3)

grp<-factor(grp)

av = aov(x1 ~ grp)

summary(av)

posthoc <- TukeyHSD(x=av,'grp',conf.level=0.95)

posthoc

R output:

summary(av)

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

grp          2 1146.3   573.2   39.14 1.12e-06 ***

Residuals   15 219.7    14.6                    

Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

> posthoc <- TukeyHSD(x=av,'grp',conf.level=0.95)

> posthoc

Tukey multiple comparisons of means

    95% family-wise confidence level

Fit: aov(formula = x1 ~ grp)

$grp

        diff      lwr            upr    p adj

2-1 12.166667   6.427796 17.90554 0.0001682

3-1 19.333333 13.594463 25.07220 0.0000008

3-2 7.166667 1.427796 12.90554 0.0141999

Calculated F=39.14, P=0.000 which is < 0.05 level of significance.

There is significant differences among the seedling heights for the three groups.

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