M$: It’s not a bug, it’s a feature! [Software]

posted by Helmut Homepage – Vienna, Austria, 2019-12-17 15:00 2a02:8388:6bc2:ce80:6c4e:e4df:42f4:6510 – Posting: # 20985
Views: 292

Hi all,

known for ages. All (‼) versions of Excel round the degrees of freedom down to the nearest integer.

df <- seq(10, 11, 0.2)
q  <- 4.5
res <- data.frame(df = df, correct = pt(q, df), Excel = pt(q, floor(df)))
print(res, row.names = FALSE)

[image]  df   correct     Excel
10.0 0.9994284 0.9994284
10.2 0.9994561 0.9994284
10.4 0.9994818 0.9994284
10.6 0.9995059 0.9994284
10.8 0.9995284 0.9994284
11.0 0.9995494 0.9995494

Quoting Martin:

Never never never never use Excel. Not even for calculation of arithmetic means.


Congratulations to M$ for making a continuous function discrete. :thumb down:

I had fun comparing papers by regulators based on Luther Gwaza’s Excel-Sheet for adjusted indirect comparisons with my R-package. Satterthwaite’s degrees of freedom are practically never* integers. Remember this goody of the EMA?

Results obtained by alternative, validated statistical programs are also acceptable except spreadsheets because outputs of spreadsheets are not suitable for secondary assessment.

Helmut Schütz

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