Yoshi Nishikawa Blog

医学となにかのインタラクティブ

論文を書く際の統計的表現について

論文執筆の際、p値はどう記載するんですか?

有効数字は?

有意差なしはNSだけでよいですか?

0.05未満は<0.05でよいのですか?

・・・

このように聞かれたり、議論になったりすることがあるので、纏めておきます。

あくまで、一例ですが、Annals of Internal Medicine (IF 17)の投稿規定は以下のようになっています。

p値は0.001より小さい場合は、<0.001、0.001-0.20は有効数字3桁、0.20より大きい場合で2桁、と書かれています。

一流誌の投稿規定は、それ自身が勉強になることが多いですね。

以下はAnnals of Internal Medicineからの引用です。

Reporting guideline

##Percentages

Report percentages to one decimal place (i.e., xx.x%) when sample size is =200. 

To avoid the appearance of a level of precision that is not present with small samples, do not use decimal places (i.e., xx%, not xx.xx%) when sample size is < 200.

##Standard deviations

Use “mean (SD)” rather than “mean ± SD” notation. The ± symbol is ambiguous and can represent standard deviation or standard error.

##Standard errors

Report confidence intervals, rather than standard errors, when possible.

##P values

For P values between 0.001 and 0.20, please report the value to the nearest thousandth. For P values greater than 0.20, please report the value to the nearest hundredth. For P values less than 0.001, report as “P<0.001.”

##“Trend”

Use the word trend when describing a test for trend or dose-response.

Avoid the term trend when referring to P values near but not below 0.05. In such instances, simply report a difference and the confidence interval of the difference (if appropriate) with or without the P value.

##Statistical software

Specify in the statistical analysis section the statistical software—version, manufacturer, and the specific functions, procedures, or programs—used for analyses.

##Cox models

When reporting findings from Cox proportional hazards models:

Do not describe hazard ratios as relative risks.
Do report how the assumption of proportional hazards was tested, and what the test showed.

##Descriptive tables

In tables that simply describe the characteristics of 2 or more groups (e.g., Table 1 of a clinical trial):

Report averages with standard deviations, not standard errors, when data are normally distributed.
Report median (minimum, maximum) or median (25th, 75th percentile [interquartile range, or IQR] when data are not normally distributed.
Avoid reporting P values as there can be imbalance when P values are not significant (because of small sample size) and balance when P values are significant (because of large sample size).

##Tables reporting multivariable analyses

Authors sometimes present tables that compare one by one an outcome with multiple individual factors followed by a multivariable analysis that adjusts for confounding. If confounding is present, as is often the case, the one-way comparisons are simply intermediate steps that offer little useful information for the reader. In general, omit presenting these intermediate steps in the manuscript and do not focus on them in the Results or Discussion.

##Figures

When developing informative graphics, follow these simple rules of thumb:
Avoid pie charts.
Avoid simple bar plots that do not present measures of variability.
For meta-analysis forest plots, provide the raw data (numerators and denominators) in the margins.
For survival plots, provide the numbers of people at risk by group and time below the horizontal axis.