"El promedio es cuatro."
Translation:The average is four.
"Average can be in mean (arithmetic mean), median, or mode."
"Promedio" maybe similar to "average" and can be expressed in same way with all of them. I think Spanish may have precise words for the mean(?), the median (la mediana), and the mode (la moda).
But in general, it can be taken as mean, as it is the most commonly used of the three.
Average is synonymous to arithmetic mean in a statistical setting, but averagealso has less precise definitions (eg "average Joe"). The two are not always interchangeable. While this does seem like a numerical statement and mean child be correct. "Average" could be the better choice due to differences in connotation. FWIF, spanishdict.com lists la media for the mean. (Spoken as somebody who made the same mistake.)
In this case "the average is four" makes no sense unless you're talking about a particular type of average, so it is correct to say mean.
No, because you have the subject and object switched. That would be "Cuatro es el promedio."
I enter the comment sections to see if anyone already has clarified Spanish words that I struggle with. But in almost every comment section the main discussion is English words.