# '2-3' or 'two to three' proper use

In the following sentence is the use of '2-3' appropriate for a PowerPoint presentation or should it be 'two to three'?

Research shows that a deaf child tends to produce signs 2-3 months earlier than hearing children’s first spoken words.

Is there a difference in the meanings between these two methods of statement?
Why is one preferred over the other, if it is?

The en-dash is used for ranges of values, such as "1994–2010," "pp. 183–652."
I find it fine to use the en-dash in such cases in a presentation.

In some cases, it could be convenient not to express a range of values using the en-dash; for example, the Guide for the Use of the International System of Units suggest not to use the en-dash if it could be confused with a subtraction, such as in "an amperage of 2–5 A."

The value of a quantity is expressed as the product of a number and a unit (see Sec. 7.1). Thus, to avoid possible confusion, this Guide takes the position that values of quantities must be written so that it is completely clear to which unit symbols the numerical values of the quantities belong. Also to avoid possible confusion, this Guide strongly recommends that the word “to” be used to indicate a range of values for a quantity instead of a range dash (that is, a long hyphen) because the dash could be misinterpreted as a minus sign. (The first of these recommendations once again recognizes that unit symbols are not like ordinary words or abbreviations but are mathematical entities—see Sec. 7.2.)—The Guide for the use of the International System of Units, page 18.

• It's hard to see how anyone could interpret "2–5 A" as "2 minus 5 amperes", because (a) although currents can flow either way, amperage is always a measure of their magnitude, not their direction, and (b) even if negative amperages were accepted, they would never be stated in this uncalculated way: it would have to be "an amperage of -3 A". Jun 27 '11 at 6:42
• @John Bentin That is what the guide reports. Jun 27 '11 at 6:56
• @JohnBentin The wall supply voltage, $v$, to a circut is guaranteed to be within 110–120 VAC. The supply is fed through the a transformer with 500 primary windings and two secondary coils of 200 and 300 windings each, giving an output of (*note, a real book would have LaTeX here - the stuf between the '$'s denotes LaTeX)$v_1 = \frac{200}{500} * v = 44–48 VAC$and$v_2 = \frac{300}{500} v = 66–72 VAC$. The resulting voltages are fed into an ideal op-amp subtraction circut, with$v_1$as the negative value. The resulting voltage is then$v_r$=$v_2 - v_1$= 66–72 - 44–48 VAC = 22–24 VAC$. Apr 20 '13 at 23:14
• @JohnBentin Not that any actual professional would do that (the circuit or the notation mistake), but this could easily happen in a low-quality textbook. Apr 20 '13 at 23:17

The two statements are equivalent. If word count or space is a consideration, use "2–3", preferably with an en dash and not a hyphen. (See this question for more info on dashes and hyphens.) If you were writing something longer, I would suggest using "two to three" or a similar phrase instead; almost all style guides suggest spelling out small numbers, although they differ on the cutoff point.

No difference in meaning, it's just that 2-3 is slightly more 'informal'.

If you were reading out the displayed text of the presentation, no-one would think it odd if you said "two or three" rather than "two to three" (I would even prefer that, since I don't like the ungainly homophonic usage).

There's nothing wrong with either "two to three" or "2-3" in this case. Either are not preferred above the other. I reckon it's just that "two to three" is more formal only. Nothing else.