Tasaka et al. (A- 61) note that Corynebacterium parvum (CP) increases susceptibi

Question

Tasaka et al. (A- 61) note that Corynebacterium parvum (CP) increases susceptibility to endotoxin, which is associated with increased production of tumor necrosis factor (TNF). They investigated the effect of CP-priming on the pathogenesis of acute lung injury caused by intratracheal Escherichia coli endotoxin (lipopolysaccharide [LPS]) Experimental animals consisted of female guinea pigs divided into four groups. Animals in two groups received a 4-mg/ kg treatment of CP 7 days before the study. Subsequently, nonpretreated animals received either saline alone (Control) or endotoxin (LPS-alone). The pretreated groups received either saline (CP alone) or LPS. Among the data collected were the following values of lung tissue-to- plasma ratio of radio-iodized serum albumin assay (variable RATIO).

What are the study questions?

What is the outcome of interest (dependent variable)?

What are the predictors of outcome (independent variables)?

What statistical model was used?

What statistical hypotheses were tested to address the study questions?

Were the null hypotheses rejected at the level 0.05?

What conclusions should be made based on the statistical analysis results?

In addition to summary questions 1-7 answer the following questions:

Is there a significant effect of CP-priming on RATIO? What is the mean difference in RATIO (with the corresponding confidence interval) due to CP-priming?

Is there a significant effect of LSP treatment on RATIO? What is the mean difference in RATIO (with the corresponding confidence interval) due to LSP treatment?

Is there a significant interaction between CP-priming and LSP treatment?

Which paired differences among 4 groups are significant at the 0.05 level and what are the corresponding confidence intervals?

The ANOVA Procedure Dependent Variable: RATIO Sum of DF Squares Mean Square F Value Pr> F Source 3 0.83228589 0.27742863 18.00

Explanation / Answer

Answer to question# 1)

The study questions are :

Does CP increase susceptibility to endotoxin

Does LPS increase susceptibility to endotoxin

Does the interaction of CP and LPS increase susceptibility to endotoxin

.

Answer to question# 2)

The dependent variable in this study is "endotoxin"

The susceptibitlity to endotoxin increases ....with the increase in CP and change in LPS

This is what the study is based on

So the variable that is dependent is the "susceptibility to endotoxin"

.

Answer to questioN# 3)

the indpendent variables are CP and LPS: each of these two independent variables have two levels

.

Answer to question# 4)

Th model used is a Two Way ANOVA model , which is used for two or more factors. Here the two factors are CP and LPS levels. It helps to understand the impact on susceptibiity to endotoxin

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