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 Thursday, June 04, 2009 #7699

We have been using the following formula to add reach from month to month for our online campaigns: (R1+R2)(R1*(R2/100))*.96. After some research on your site, the initial part of the formula seems to be the formula for random probability but I'm not sure where the multiplying it by .96 came from. Any thoughts? Could that be another estimate on duplication?
 The Media Guru Answers(Saturday, June 06, 2009 ):

Applying a factor like "0.96" is an old technique to adjust random duplication (which, as you say, is the first part of your formula) for the fact that duplication in some cases is somewhat greater than simply random.
Between different media, such as print and tv, it is thought to be truly random, that is, there is no greater likelihood that a newspaper reader of your campaign will see your tv campaign, than any other two random events. However, between two elements of the same medium, like two TV dayparts, there is a more than simply random chance of duplication.
That is the traditional case for using a factor like 0.96.
Between consecutive time periods of the same medium, as in your case, the Guru expectss a much greater chance of duplication. You are looking at new exposures of the same vehicle, which should be represented as accumulating along one sharply flattening asymptotic curve (see below). It's a "cume," not a "combination." Random combination is far too optimistic. Unduplicated users from the first few months to the next added would probably become virtually total unless each month used unique, unrelated sites.
 Tuesday, September 02, 2008 #7587

Dear MG! Can you explain to me  is it any differense between calculating Recah 1+ in media mix (by random probability) and Reach 2+,3+ and so on, or we can use the same sheme as for Reach 1+? Thank you a lot!
 The Media Guru Answers(Thursday, September 04, 2008 ):

It's quite different.
Assuming you are talking about
combining media, in the new 2+ group,
you will have some of the two+ from the
1+ group in medium A
, some from the original 2+ group some
from the same sets in medium B and so on. It's a complex formula.
 Thursday, July 17, 2008 #7568

Hello Media Guru 
I am trying to figure out the best way to combine national magazine reach and national internet reach. I know that I can use the random probability formula to combine two reach numbers. However, the problem I keep running into is that my base for print reach is total US (based on MRI numbers) and my base for internet reach is total US that is online (based on comScore numbers). Any suggestions on how to combine these numbers? Thanks!
 The Media Guru Answers(Thursday, July 17, 2008 ):

 Determine what % of your target is in the online universe, say it's 70%
 Multiply this factor against your internet reach. That is, if your internet reach is 50%, you are reaching 70% of that number on a total US basis. 50% X 70% = 35%
 Now you can combine your 35% internet US reach with your print reach by random probability. Apply the same universe factor to GRP. Internet frequency will not change
 Monday, May 28, 2007 #7339

What is the "Sainsbury" formula and is there a difference between unique circulation and paid circulation? Thank you!
 The Media Guru Answers(Monday, May 28, 2007 ):

The Sainsbury formula is a method for combining the reaches of schedules in different media. It varies from the simple random probability method which is based on the generally accepted assumption that there is no particular correlation between exposure to one medium and another. Sainsbury varies by adding a small adjustment to account for an assumed slightly morethanjustrandom probability that those exposed to an advertiser's schedule in one medium will also be exposed to its schedule in the next medium. Typically, the adjustment is about a 5% deduction from the result of the random combination.
As you will see at the link shown, we may vary in our arithmetic expression of the probability equation (for the same result), so we can express the Sainsbury formula as (0.95 x random probability).
Unique circulation and paid circulation are unrelated terms.  Paid circulation refers to the number of copies which are actually bought for money at the newsstand or by paid subscription, rather than distributed free or at such a discounted rate that the circulation auditor no longer qualifies the copies as "paid."
 "Unique" is more commonly an intrnet audience term. Perhaps you are thinking of "unduplicated" audience which only counts readers once, if they read two or more issues.
 Wednesday, February 09, 2005 #6787

What is the formula for combining two R&Fs?
 The Media Guru Answers(Wednesday, February 09, 2005 ):

Click here to see past Guru responses about "random probability"
 Monday, February 04, 2002 #5050

Is Telmar's multibasing system the same thing as Fusion? And, if I'm currently doing the random probability formula to get total reach percent, what is the difference between that and Telmars calculations? Thanks.
 The Media Guru Answers(Wednesday, February 06, 2002 ):

According to Telmar:
Multibasing preserves the integrity of a survey. It does not ascribe
answers, and as such, avoids what we call "regression to the mean",
washing away everything to averages. It preserves the leverage of a media
element against any target group, not just those that leverage on
demographics.
Telmar's R&F formulas use the actual turnover and duplication
between media that are inherent in the survey. When there is real
data, we use it.
 Friday, June 29, 2001 #4538

Hello again,
I have two questions about calculating reach and frequency that I have been unable to find in the archives of past responses. Perhaps you can help?
1. I normally use the formula (a+b)(.a*b) to determine combined reach of two mediums, such as radio and print. How do I calculate the combined reach of more than two? The plan I am working on includes spot TV, spot radio and local newspaper.
2. Is it possible to determine a combined reach for more than one market or should each market be reported separately? In the past, I have provided separate delivery for each market in the same plan with a total number of gross impressions for the whole plan. Is this correct?
Thanks in advance!
 The Media Guru Answers(Friday, June 29, 2001 ):

1. This common formula is based on an assumption that different media duplicate their audiences according to random probability. Therefore if you follow this assumption, media may be added to combinations of media in a "chain" of the same formula. So, once you have combined TV and Radio, you can use this combination as your "a" and then combine it with newspaper as "b."
2. You can combine reaches across markets by doing a weighted average. Multiply the reach in each market by the percent of U.S. in each market. Add all the products and divide by the sum of the % U.S.
 Thursday, March 16, 2000 #3326

Dear Guru:
I would like to know if there is any equation to calculate media mix reach?
 The Media Guru Answers(Thursday, March 16, 2000 ):

There are several, equivalent ways to express the arithmetic to combines media according to random probability, which has been found generally adequate for the purpose of multimedia combination.
Here's an easy one:  Work with two reaches at a time
 Treat the reach of each medium as a decimal (50 reach is 0.5)
 Add reach of medium A and medium B
 Multiply reach of medium A by Reach of medium B
 Subtract the product of the multiplication from the sum of the addition
Example:  Reach of medium A = 40, reach of medium B = 55
 0.4 + 0.55 = 0.95
 0.40 x 0.55 = 0.22
 0.95  0.22 = 0.73
 Combined reach is 73
To add additional media, treat the combination as medium A and the next medium as B.
In some cases, a planner may have access to research which shows that an adjustment should be made for actual, measured, duplication between different media, rather than use the "random probability" formula above. In that case, more sophisticated reach calculating software packages, such as those from
Telmar allow you to make the calculation and build in known adjustments.
 Tuesday, September 14, 1999 #2792

What can you tell me about reachbased planning?
Thank you in advance.
 The Media Guru Answers(Tuesday, September 14, 1999 ):

>
The usual assumption is that print and broadcast duplicate with random probability, there is no special, greater or lesser likelihood that persons in the audience of the print schedule will also be or not be in the audience of the broadcast schedule.
Mechanically. the combination may be calculated in a few equivalent ways. The Guru finds it easiest to consider the reaches as decimals (50% reach = 0.50). Subtract the reach of print from 1 and multiply this by 1minus the reach of broadcast. Suppose print has a 40% reach and broadcast has 55%. By subtracting 0.4 from 1 (1  0.4 = 0.6), you have the probabilty of the target not being exposed to print. Subtract 0.55 from 1 to get the probability of not being exposed to broadcast (1  0.55 = 0.45)
Multiply these two together (0.6 * 0.45 = 0.27) and you have determined there is a 27% probability of people not being exposed to either of the combined media, or a 73% reach.
This formula is typically used in media software to combine different media. Certainly there are cases where there is a somewhat better than random probabilty of media duplication, such as TV Guide combining with a TV schedule, but that's the exception, calling for judgement.
 Wednesday, September 01, 1999 #2759

Is the random probability formula used to combine reach for different media also valid when looking at effective reach (i.e. 4+ level)?
 The Media Guru Answers(Thursday, September 02, 1999 ):

If you mean, can you combine the 4+ reach of one medium with the 4+ reach of another medium to get the 4+ reach of the two combined media, the answer is no.
Among those who were reached 2 or 3 times by each medium, some will now be reached 4 or more times and some will not, yet these people are not considered by combining only the two four+ groups. There are also those reached only once by the first medium and three times by the other, etc. A new, overall calculation of the frequency distribution must be done, to determine the 4+ of the combination.
 Friday, April 30, 1999 #2481

Is there any way to calculate duplication across a media plan using several media (e.g. print and radio and TV), or can I only get a duplication analysis within a media (radio duplicaton and then another duplication factor for print, etc , etc)
I use telmar for research with simmons and arbitron access and we also use JDS for buys.
 The Media Guru Answers(Friday, April 30, 1999 ):

The standard assumption in media planning is that duplication between different media is purely at random. Therefore, the random probability formula is used:
 Express the reach of each medium as a decimal (50% reach = 0.5)
 Multiply the reach of one medium by another to determine the duplication.
 Subtract the duplication from the sum of the two reaches to get the net reach
So, if you have a 40% reach in TV and a 55% reach in Print, multiply
0.4 x 0.55 to get 0.22
subtract 0.22 from 0.4+.55 and get 0.73 or 73% reach of the combined media.
There are a variety of ways to do the calculation. The Guru actually prefers to use the probablilty of not seeing each medium (reach as a decimal subtracted from 1.0) When these are multiplied they give the net probability of not seeing any of the media. When this result is subtracted from 1, the final result is net reach. This style is particulary useful for combining several media at once.The example would combine this way:  10.4 = 0.6
 10.55 = 0.45
 0.6 x 0.45 = 0.27
 10.27 = 0.73 or
73% reach.
Telmar's "Media Mix" program uses these assumptions.
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