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Wednesday, February 24, 1999 #2355
How to read a crosstab

The Media Guru Answers(Wednesday, February 24, 1999 ):
The Guru has just posted a detailed, graphic explanation of how to read a crosstab. It's just down the page at Query # 2346, from Feb. 17. Or Click here to see past Guru responses on "crosstab"

Wednesday, February 17, 1999 #2346
Could you please provide the basics on how to read a crosstab? Also, the definitions of the terms %col, row, composition, coverage, index - what do all of these mean? This would be very help to folks who are new to media planning and research, so that they could explain crosstab results to others. Thank you!

The Media Guru Answers(Wednesday, February 17, 1999 ):
crosstabs, those typical computer analyses of data from MRI, Simmons, The Mendelsohn Media Research Affluent Study and other respondent databases, are an essential tool of media planning, used for target selection, media selection, etc.

Here is a section of a typical "crosstab," taken from The Mendelsohn Media Research Affluent Study Reflecting Households with Income of $70,000 plus . It concerns Cosmetics users, persons who visited the Caribbean and Vodka drinkers:

To the left, first the description of each row appears. The top "row," which consists of five lines of data, describes the total population. The next "row" of five lines of data describes readers of Money Magazine, etc.

The next sets of text to the right describe the data content of each of the five lines making up the data rows. "Projection" is the total number of persons the research estimates to be in each category (in thousands, in the total adult universe, which is specified at the top left of the table. This is sometimes labeled "[000]"). Often the term "Audience" appears instead of Projection, especially, though not exclusively, when magazine audience is being analyzed).

The column headings, such as "Total," "Cosmetics," " Drink Vodkas" etc, describe the data in the columns below each heading.

So, at the #1 mark, we learn that 24,855,000 Total affluent adults used Cosmetics in the past year.

At the #2 mark, we see that the number of respondents (persons in the sample) whose educational level is college graduate or better and who use Cosmetics is 3469. In other words, the overall study found 3467 members of its sample who fit both descriptions as to education and cosmetics use. It is important to note this is a whole number and not in thousands. The number 12295 above this indicates that, from this sample, the study projects there are 12,295,000 college (or better) educated cosmetics users.

At the #3 mark we see 12.4 on the %Column line. This means that 12.4% of the column definition (Vodka Drinkers) also fit the row description (Money Magazine readers), that is, 12.4% of Vodka Drinkers read Money. Another way we refer to this is to say that Money's coverage of Vodka Drinkers is 12.4%

At the #4 mark, "%Row" is 16.0, so we learn that 16.0% of the Row definiton (Money readers) drink Vodka. Or, we can say that Money's Vodka Drinker composition is 16.0%

Finally, at the #5 mark, we have an index of 131.3. This is also called "index of selectivity," indicating how much more likely, as compared to the average affluent adult, the persons in the row are to also be in the column. (Traditionally indices are used with no decimal places, so, in application, one would refer to this in future use as a "131 index.")
In this case, the index tells us that a person in a Household which has $100,000 or higher income is 31.3% more likely to have taken a Caribbean trip than the average affluent adult. The index can be calculated either dividing the %Column under Caribbean visit by the %Column under total:
in the Caribbean visit column, dividing the %Row in HHI $100,000+ by the %Row in the "Total" row: