[R] Wrong results from anova

[Phil Spector]

Li Li -
    I belive it's a rounding error -- try setting

options(digits=8)

    before displaying the output:

> summary(fit.Y)
             Df Sum Sq Mean Sq F value Pr(>F) 
sample.Y     3   2203     734  190706 <2e-16 ***
Residuals    8      0       0 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> summary(fit.Y)
             Df  Sum Sq Mean Sq F value    Pr(>F) 
sample.Y     3 2202.70  734.23  190706 < 2.2e-16 ***
Residuals    8    0.03    0.00 
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu




On Tue, 14 Apr 2015, li li wrote:

> Hi all,
>  I have following data. When I perform an anova, the residual sum of
> square returns to be zero.
> But this is wrong, since we can hand calculate the RSS to be around 0.0308.
>  Did anyone come across the same problem before? Any suggestions?
>  Thanks.
>    Hanna
>
>> ydata
>        Y sample.Y
> 1   0.477      0.5
> 2   0.477      0.5
> 3   0.478      0.5
> 4  27.320       27
> 5  27.420       27
> 6  27.300       27
> 7  29.440       29
> 8  29.620       29
> 9  29.610       29
> 10 35.840       35
> 11 35.900       35
> 12 35.850       35
>> fit.Y <- aov(Y~sample.Y, data=ydata)
>> summary(fit.Y)
>            Df Sum Sq Mean Sq F value Pr(>F)
> sample.Y     3   2203   734.2  190706 <2e-16 ***
> Residuals    8      0     0.0
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
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