Q. Help! I have been trying to potty train our 2 1/2-year-old daughter for almost a month.

She started to stay dry after about four days, getting a jellybean and lots of praise for each success. She was dry for about a week and then she started telling us less and less often when she had to go.

She does tell us she must go when she wakes up -- she sleeps dry through the night -- but that is the last time she asks to use the potty all day unless we're putting her down for her nap. This is a great stalling technique, but at least she uses the potty then. Otherwise, she doesn't use it at all if we don't take her to it at the right time.

Because the accidents increased, I have put her back in diapers but she often says she doesn't want to wear them -- and then she wets. For what it's worth, she will tell us if she's dry or wet when she's changed.

Also, she has a 6-month-old sister. Could this be bothering her?

A. New little sisters (and little brothers) always bother older children but usually not enough to cause a potty-training problem. It's more a matter of timing and maturation.

Fifty years ago many doctors told parents to monitor their infants carefully and they'd know just when to put them on the pot. And it worked. The parents, if not the children, were soon well trained.

Now doctors think 3 is a fine age to train a child, but many parents want to train them a good deal sooner. And it can be done. Some children can be trained between 18 months and 2 but only if the nerve connections are mature enough for the sphincter muscles to work well.

This maturity is generally achieved by 2 1/2 and your little girl has reached it: She stays dry all night, she asks to use the potty and she tells you when she's wet or dry.

So why is she having accidents? For the most simple reason of all: She is 2 1/2.

The need for independence is inborn and universal and this is the year she pursues it. It gives her the underpinning she needs to keep growing in a healthy way and it is much more important than toilet training.

Now she is learning how to be her own person. Most children find this hard to do and the more orders they're given, the harder it becomes. It's hard for a child to feel independent and still use the pot when she's told -- and to wear shoes and sit in the stroller and eat her peas and follow all the other orders she gets every day. Consequently, 2-year-olds (as well as 2 1/2s) follow as few orders as possible, which is why they should get only the necessary ones.

This isn't a prescription for permissiveness but a way to avoid needless rebellion. Every line you draw in the dust challenges the 2-year-old to jump across it. In another six months, your child will be 3 and should feel independent to the point of complacency. This will make toilet training a cinch.

Since your little girl is physically ready to be trained -- or she wouldn't have been dry for a week -- and since she doesn't like diapers any more, you may not want to wait that long.

Toilet training should work now if you're very matter-of-fact about it and if she wears simple clothes she can pull down herself. Continue to put her on the potty in the morning, before her nap and whenever she asks, but she will still have to be prompted. It's best to let an alarm clock do the prompting for you by setting the clock about five times during the day, probably a half-hour after meals and after morning and afternoon snacks. At this age a child may find it easier to obey an inanimate object than a parent.

When the clock rings, walk her to the pot -- to make sure she gets there -- and perhaps read to her while she sits. Koko Bear's New Potty by Vicki Lansky (Bantam, $3.50) is a good choice because it has some parenthetical advice for you.

Take her off the pot in 5 or 10 minutes -- or sooner if she's restless -- and congratulate her for trying, whether she's been successful or not. Praise is important but forget about outrageous praise or small bribes. Jellybeans, as you've discovered, soon become a bore. She just needs to know that you're proud of her for trying to be a big girl.

There will be accidents, of course -- quite a few of them -- but if you take care of them without a fuss or even much of a mention she will keep trying to improve.

And if she's not quite ready to be such a big girl, go back to diapers during the day, or at least when you go out. Otherwise, too many accidents may turn toilet training into a power struggle between you.

With this technique, your child should be well-trained by the time she is 3. If not, put on your no-nonsense hat, say, "That's it, kiddo!" and promise her a trike when she's trained, because then you'll know she's really a big girl. This will have her wearing dry underpants within a week and she'll be just as pleased about it as you are.

If you're going to use bribery, wait until she's a more receptive 3 -- and make it worth her while.

bybio Questions may be sent to Family Almanac, P.O. Box 15310, Washington, D.C. 20003.