Question

In a hypothetical in vivo study, expression levels of gene UNK in kidney have been measured in rats treated with vehicle (control group) as well as in animals treated with low and high doses of a drug candidate. The levels of the UNK transcript (in arbitrary units) in the animals that survived until the end of the study are shown below. The investigators ran one-way ANOVA on their data (also shown below), and based on the obtained result a conclusion has been drawn about the lack of significant association between the drug dose and expression level of UNK.

Please comment on the merit of this finding.

subj.id <- c("01952", "01781", "01745", "01674",
             "01937", "01762", "01402", "01938",
             "01465", "01471", "01479", "01729",
             "01527", "01945", "01071", "01220",

             "01506", "01192")
unk.expr <- c(1.44, 1.03, 2.02, 0.21, 1.49, 5.97,

              2.02, 0.96, 2.49, 1.46, 3.51, 3.68,

              1.52, 0.83, 0.69, 2.41, 0.61, 1.48)
drug.dose <- c("veh", "low", "high", "veh", "veh",

               "veh", "low", "veh", "low", "low",
               "high", "high", "veh", "veh", "veh",
               "low", "veh", "veh")

drug.dose <- factor(drug.dose,c("veh","low","high"))
anova(lm(unk.expr~drug.dose))

Analysis of Variance Table

Response: unk.expr
          Df  Sum Sq Mean Sq F value Pr(>F)

drug.dose  2  5.5443  2.7721  1.5359 0.2473
Residuals 15 27.0739  1.8049

Answer 1

Using one way ANOVA

Assumption of test it shows the statistic and sample size of rats and other animals..

They used variances,null hypothesis (Ho) and alternative hypothesis (Ha) is shows low,high,vehicle doses among control group.drug dose UNK transcript shows the result is animals survived until the end of the study..

Hi and Happy not equal vary in dose low,high and vehicle..Test of Homogeneity of variance.

P value is trigger than alpha value,because the equal variances are assumed.

Ho = low,high,vehicle doses are accepted.

Since the sample size are very different between rat and other animals..

ANOVA was statistically significant there is difference between gene UNK in kidney..