HP-25 statistics weirdness

[Thomas Klemm]

I could imagine that \(\sum y\) and \(\sum xy\) can still be useful in case of a frequency table.
You can interpret \(y\) as frequency and \(x\) as value.

The mean is then:

\(
\bar{x} = \frac{\sum xy}{\sum y}
\)

Example:
\(
\begin{array}{|c|c|}
\hline
Frequency & Value \\
\hline
3 & 7 \\
5 & 11 \\
2 & 13 \\
\hline
\end{array}
\)

CLEAR REG
3 ENTER 7 \(\Sigma +\)
5 ENTER 11 \(\Sigma +\)
2 ENTER 13 \(\Sigma +\)

RCL 5
RCL 4
\(\div\)

10.20