In Microsoft Word you can type the null hypothesis symbol, which is the letter H followed by the numeral 0 as a subscript using the subscript button in the Home tab, or you can use a keyboard shortcut to apply the subscript format. Note that after typing the zero as a subscript, any punctuation immediately after it will also appear as a subscript unless you disable the subscript formatting.
Typing the Symbol
To type the null hypothesis symbol, type the letter "H" and then click the subscript icon in the Font section of the Home tab. Your cursor will appear smaller, and you can now type the numeral "0." When you press the space bar, your font will change back to your default font size and you can continue typing.
Using a Keyboard Shortcut
After you've typed the letter "H," press and hold the Ctrl key, then press the equal sign and then release both. You can now type the numeral "0," which will appear as a subscript. When you press space, your font size will revert to what it was formerly and you can continue typing.