How to deal with intraday prices conflicting with EOD highs and lows
"In the US, stocks are listed on one exchange but can be traded on multiple venues.  You need to confirm exactly what your data is showing: a) trades on the primary-listed exchange; or b) trades made at any venue. Also, the trade condition codes are important.  Only certain trade condition codes contribute towards the day's open/high/low/close and some others only contribute towards the volume data.  The Consolidated Tape Association is very clear on which trades should contribute towards each value - but some vendors have their own interpretation (or just simply an erroneous interpretation of the specifications). It may surprise you to find that the majority of trading volume for many stocks is not on their primary-listed exchange.  For example, on 2 Mar 2015, NASDAQ:AAPL traded a total volume across all venues was 48096663 shares but trading on NASDAQ itself was 12050277 shares. Trades can be cancelled.  Some data vendors do not modify their data to reflect these busted trades.   Some data vendors also ""snapshot"" their feed at a particular point in time of the data.  Some exchanges can provide data (mainly corrections) 4-5 hours after the closing bell.  By snapshotting the data too early and throwing away any subsequent data is a typical cause of data discrepancies.   Some data vendors also round prices/volumes - but stocks don't just trade to two decimal places. So you may well be comparing two different sets of trades (with their own specific inclusion rules) against the same stock.  You need to confirm with your data sources exactly how they do things. Disclosure: Premium Data is an end-of-day daily data vendor."
You said the decision will be made by EOD. If you've made the decision prior to the market close, I'd execute on the closing price.  If you are trading stocks with any decent volume, I'd not worry about the liquidity.  If your strategy's profits are so small that your gains are significantly impacted by say, the bid/ask spread (a penny or less for liquid stocks) I'd rethink the approach. You'll find the difference between the market open and prior night close is far greater than the normal bid/ask. If you are in it for the long run and are not worried about intra day fluctuations and buying within + or - 1% you would be better off going for a market order as this will make sure you buy it on the day.  If you use limit orders you risk missing out on the order if prices gap and start rising in the morning. Another option is to employ stop buy trigger orders (if offered by your broker). So you would have to sum up and decide which type of order would suit your strategy the best. Are you looking to buy the security because you are looking for long term growth and gains, or are you after getting the best price possible to help your short term gains? There are lots of reasons for the differences in price. Can you go to (a) bank, (b) forex bureau and (c) central bank and post back both bid and offer prices at a given time so we can consider the spread? What you've said above for (a) and (b) are presumably USDGHS offer prices, because they are higher than the (c) central bank price. If a bank or bureau bid price was higher than the central bank offer price then you could buy GHS from the central bank and then sell them to a bureau for a higher price, an almost no risk arbitrage, other than the armoured car to deliver the funds from central bank to bureau. What you've posted is: (a) a bank will sell you 1 USD for 3.4 GHS (b) a bureau will sell you 1 USD for 3.7 GHS (c) we can see the bid/offer for central bank is 3.1949/3.1975 which means the central bank, if you have an account, will sell you 1 USD for 3.1975 GHS. You clearly want to buy USD from the central bank, then the bank, then the bureau. Anyway, the reason for these differences is all to do with liquidity conditions in the local areas, the customer types, and the frequency of orders versus inventory... Think about it. The central bank has the most frequency of orders and the biggest customers so it offers the lower price, then the bank, and then the bureau. I think the bureau is the worst price there... You have to explain further :) You typically need to specify that you want the GTC order to be working during the Extended hours session. I trade on TD Ameritrade's Thinkorswim platform, and you can select DAY, GTC, EXT or GTC_EXT. So in your case, you would select GTC_EXT. In my experience thanks to algorithmic trading the variation of the spread and the range of trading straight after a major data release will be as random as possible, since we live in an age that if some pattern existed at these times HFT firms would take out any opportunity within nanoseconds. Remember that some firms write algorithms to predict other algorithms, and it is at times like those that this strategy would be most effective. With regards to my own trading experience I have seen orders fill almost €400 per contract outside of the quoted range, but this is only in the most volatile market conditions. Generally speaking, event investing around numbers like these are only for top wall street firms that can use co-location servers and get a ping time to the exchange of less than 5ms. Also, after a data release the market can surge/plummet in either direction, only to recover almost instantly and take out any stops that were in its path. So generally, I would say that slippage is extremely unpredictable in these cases( because it is an advantage to HFT firms to make it so ) and stop-loss orders will only provide limited protection. There is stop-limit orders( which allow you to specify a price limit that is acceptable ) on some markets and as far as I know InteractiveBrokers provide a guaranteed stop-loss fill( For a price of course ) that could be worth looking at, personally I dont use IB.  I hope this answer provides some helpful information, and generally speaking, super-short term investing is for algorithms. "If the stock is below its purchase price, there is no way to exit the position immediately without taking losses. Since presumably you had Good Reasons for buying that stock that haven't changed overnight, what you should probably do is just hold it and wait for the stock to come back up. Otherwise you're putting yourself into an ongoing pattern of ""buy high, sell low"", which is precisely what you don't want to do. If you actually agree with the market that you made a mistake and believe that the stock will not recover any part of the loss quickly (and indeed will continue going down), you could sell immediately and take your losses rather than waiting and possibly taking more losses. Of course if the stock DOES recover you've made the wrong bet. There are conditions under which the pros will use futures to buffer a swing. But that's essentially a side bet, and what it saves you has to be balanced against what it costs you and how certain you are that you NOW can predict the stock's motion. This whole thing is one of many reasons individuals are encouraged to work with index funds, and to buy-and-hold, rather than playing with individual stocks. It is essentially impossible to reliably ""time the market"", so all you can do is research a stock to death before making a bet on it. Much easier, and safer, to have your money riding on the market as a whole so the behavior of any one stock doesn't throw you into a panic. If you can't deal with the fact that stocks go down as well as up, you probably shouldn't be in the market." The best thing to do is not worry about what time is best to buy but put in a conditional order before the market opens. If your conditions are met during the trading day your order will go through and you will buy the shares. This keeps your emotions out of your trading and will stop you from either chasing the market or buying when you consider the wrong time. As you have already done your analysis and made your decision before market open, thus you should place your conditional orders and stop losses before market opens as well. You're realizing the perils of using a DCF analysis.  At best, you can use them to get a range of possible values and use them as a heuristic, but you'll probably find it difficult to generate a realistic estimate that is significantly different than where the price is already. Stop orders and stop limit orders typically do not execute during extended hours after the general market session has closed. Stop orders are market orders and market orders especially are not executed during extended hours. Although there are exceptions because a broker can say one thing and do another thing with the way order types are presented to customers vs what their programming actually does. The regulatory burden is a slap on the wrist, so you need to ask the broker what their practices are. Orders created during normal market hours do not execute in extended sessions, different orders would have to be made during the extended session. Your stop order should execute if the normal market hour price stays below your stop price. So a stop limit would actually be worse here, because a stop limit will create a limit order which may never get hit (since it is above the best bid best ask) If you are looking to go long (buy) you would use bid prices as this is what you will be matched against for your order to be executed and a trade to go through. If you are looking to go short (sell) you would use the ask prices as this is what you will be matched against for your order to be executed and a trade go through. In your analysis you could use either this convention or the midpoint of the two prices. As FX is very liquid the bid and ask prices would be quite close to each other, so the easiest way to do your analysis is to use the convention I listed above. The situation you're proposing is an over-simplification that wouldn't occur in practice. Orders occur in a sequence over time. Time is an important part of the order matching process. Orders are not processed in parallel; otherwise, the problem of fairness, already heavily regulated, would become even more complex. First, crossed and locked markets are forbidden by regulators.  Crossed orders are where one exchange has a higher bid than another's ask, or a lower ask than another's bid.  A locked market is where a bid on one exchange is equal to the ask on another.  HFTs would be able to make these markets because of the gap between exchange fees. Since these are forbidden, and handling orders in parallel would ensure that a crossed or locked market would occur, orders are serialized (queued up), processed in order of price-time priority. So, the first to cross the market will be filled with the best oldest opposing order. Regulators believe crossed or locked markets are unfair.  They would however eliminate the bid ask spread for many large securities thus the bid-ask cost to the holder. Yes, the ADR will trade on a separate exchange from the underlying one, and can (and does) see fluctuations in price that do not match the (exchange corrected) fluctuations that occur in the original market. You are probably exposing yourself to additional risk that is related to: The dynamics of different contracts and liquidity can be quite different on the last day on the month and for intraday trade make sure you use bid-ask data as opposed to historical trades.  I'm not saying whether it works or not, but im just giving you ideas to improve your testing. The closest I can think of from the back of my head is http://finviz.com/map.ashx, which display a nice map and allows for different intervals. It has different scopes (S&P500, ETFs, World), but does not allow for specific date ranges, though. "Here is how I would approach that problem: 1) Find the average ratios of the competitors: 2) Find the earnings and book value per share of Hawaiian 3) Multiply the EPB and BVPS by the average ratios. Note that you get two very different numbers.  This illustrates why pricing from ratios is inexact.  How you use those answers to estimate a ""price"" is up to you.  You can take the higher of the two, the average, the P/E result since you have more data points, or whatever other method you feel you can justify.   There is no ""right"" answer since no one can accurately predict the future price of any stock."