Woodward & Lothrop will begin testing a J. P. Stevens & Co. electronic sales clerk to peddle sheets and towels in three Woodies stores next month.

The test is part of a national experiment by the textile manufacturer to see how effective the device may be as a marketing aid. Other stores using the device on an experimental basis are Filene's stores in Boston and Dillard's in Dallas.

Instead of walking into the store, rummaging around to find towels that match the bathroom tile, carrying them over to the clerk, paying for them and taking them home, the customer will be confronted by a customized display unit.

"What the lady would see," said J. P. Stevens audio-visual producer Tom Sales, "is a large TV monitor facing her." The monitor would welcome the customer to "Stevens Bed-Bath Fashion" and instruct the customer to push the "go" button.

Having done so, the customer would be asked to choose among nine categories including color sheets, print sheets, sheets with flower and lace, childrens' rooms and do-it-yourself headboards. Once the customer selects a category, the customer will be shown a one-to-three minute segment displaying the choices within the category.

At the end of the segment, all the choices will be displayed on the screen at once, and the customer will hit the number of the selection made. After that choice is made, the customer will turn to another monitor which will ask how many items the customer wants, quote prices, ask about color selection and monograms and whether the buyer wants something else.

Then the customer will confirm the order, punch in a telephone number and get the receipt from a printer. The customer takes the receipt to a clerk at a cash register to pay for the item, which will be delivered within 10 days.

"It takes a little bit longer, but it really is an opportunity to giver her the customer a complete sale," said Sales. He also said that Stevens would probably shorten some of the segments.

Jim Wells, senior vice president for marketing at Woodies, said that the advantage to the custsomer is "the complete and total selection of the Stevens product" and the advantage of the item never being out of stock. "The other advantage of the computer is it's great for gifts" and allows them to be sent easily to another part of the country, he said.

Wells said he expects the Stevens electronic sales device, which will be tested for six months, to have virtually no impact on sales of other lines of bed and bath linens.

"We mainly see this as something we're looking into that we may be able to do for our customers with our merchandise here," said Robbie Snow, a spokeswoman for Woodies. She said that the device would not reduce the workforce and that three employes are being trained to operate it.