Usage
statcheck(x, stat = c("t", "F", "cor", "chisq", "Z"), OneTailedTests = FALSE,
alpha = 0.05, pEqualAlphaSig = TRUE, OneTailedTxt = FALSE,
AllPValues = FALSE)
Arguments
stat
"t" to extract t-values, "F" to extract F-values, "cor" to extract correlations, "chisq"to extract chi-square values, and "Z" to extract Z-values.
OneTailedTests
Logical. Do we assume that all reported tests are one tailed (TRUE) or two tailed (FALSE, default)?
alpha
Assumed level of significance in the scanned texts. Defaults to .05.
pEqualAlphaSig
Logical. If TRUE, statcheck counts p
OneTailedTxt
Logical. If TRUE, statcheck searches the text for "one-sided", "one-tailed", and "directional" to identify the possible use of one-sided tests. If one or more of these strings is found in the text AND the result would have been correct if it was a one-sided test, the result is assumed to be indeed one-sided and is counted as correct.
AllPValues
Logical. If TRUE, the output will consist of a dataframe with all detected p values, also the ones that were not part of the full results in APA format
What does statcheck find?
Statcheck uses regular expressions to find statistical results in APA format. When a statistical result deviates from APA format, statcheck will not find it. The APA formats that statcheck uses are: t(df) = value, p = value; F(df1,df2) = value, p = value; r(df) = value, p = value; [chi]2 (df, N = value) = value, p = value (N is optional, delta G is also included); Z = value, p = value. All regular expressions take into account that test statistics and p values may be exactly (=) or inexactly (< or >) reported. Different spacing has also been taken into account. When checking the results of a z test in statcheck, add a space before the z. This is a bit of a hack that was added to make sure that only actual z tests in articles are recognized, and that no other strings are mistaken for a z test. So instead of running statcheck("z = 1.23, p < .05"), run statcheck(" z = 1.23, p < .05"). Extracting and testing from articles
The function statcheck can be used if the text of articles has already been imported in R. To import text from pdf files and automatically send the results to this function use checkPDFdir or checkPDF. To import text from HTML files use the similar functions checkHTMLdir or checkHTML. Finally, checkdir can be used to import text from both PDF and HTML files in a folder. Note that the conversion from PDF (and sometimes also HTML) to plain text and extraction of statistics can result in errors. Some statistical values can be missed, especially if the notation is unconventional. It is recommended to manually check some of the results. PDF files should automatically be converted to plain text files. However, if this does not work, it might help to manually install the program "pdftotext". You can obtain pdftotext from http://www.foolabs.com/xpdf/download.html. Download and unzip the precompiled binaries. Next, add the folder with the binaries to the PATH variables so that this program can be used from command line.Rounded test statistics
Also, note that a seemingly inconsistent p value can still be correct when we take into account that the test statistic might have been rounded after calculating the corresponding p value. For instance, a reported t value of 2.35 could correspond to an actual value of 2.345 to 2.354 with a range of p values that can slightly deviate from the recomputed p value. Statcheck will not count cases like this as errors.