There are two methods for doing this. Both are pretty simple and straightforward. There is the manual method documented below. There is also an automated method: right-click in chart and choose "Scrub Data". Start with a light scrub and see if that solves the problem. If not, you can either try a heavier scrub or the manual method below. There is a button on the chart toolbar labeled "Edit/Delete Bar/Tick Data" (7th from bottom on right column). It's the black candle with the red X through it. When you get a bad tick in your chart, you should be able to quickly remove it using the following process. Click on this toolbar button, then click directly on the bar which contains the bad tick. The result should be a view/edit window containing the ticks that composed that bar. Click on the "Last" column heading once or twice to quickly sort the list of ticks by price, so that you can quickly find the extreme price that is causing the problem. Once found, place your cursor in the date/time field just to the left of this price, and then hit the delete key on your keyboard. This should correct your chart.
If the bad tick didn't show up, maybe you clicked on wrong bar. You can also drag a rectangle around a group of bars to increase your chances of finding the bad tick (as opposed to just clicking on one bar). This process may seem involved, but it's really a 2 second operation once you get the hang of it. 4 quick mouse clicks and a strike on the delete key.
Another option is to turn on the tick filtering option, and have Investor/RT weed out bad ticks before they reach the charts. Tick filtering can be turned on by going to "Setup: Preferences: General". A filtering preferences checkbox can be found towards the bottom of this dialog with the format: Ignore ticks with move >= X and percent move >= Y % The values for X and Y need not be integral, e.g. X = .5 and Y = 3.3 would cause Investor/RT to filter out incoming ticks which differ from the preceding tick in price by more than 50 cents where the distance in price from the prior tick exceeds 3.3 percent. RTL token BADTK can be used to reference the number of bad ticks filtered out for any instrument. For example, run the scan formula "BADTK > 0" to see a list of tickers with one or more bad ticks and the bad tick count for each one.
Also, if your data service seems to be transmitting many bad ticks, it may be time to consider switching to another data service. A switch may help a great deal. That is the main reason why we developed Investor/RT with the flexibility to work with multiple data services. Also, I've had several users recently express to me that simply switching data feeds made a world of difference, as if they were using a completely different software product.