Home | Clinical Café Archive | June 2007

“A Table is Worth...”

June 2007 Clinical Café
By Jeff Evans, MS, CCC-SLP

Being seated at a good table in a cafe is important to some people. To them, the ambiance is an important part of the meal. Other cafe patrons could care less about their table; they’re there for the food.

How about when you open the manual of your test? Are the tables important? Absolutely. The purpose of tables is to present test-related data to you in a clear and unambiguous manner. The presence and quality of tables offer you clues to the quality of the data and the quality of the entire test product. Obscured or missing data do and should raise red flags.

Standardization Sample Tables

The normative sample is the part of the population used to standardize a test. The normative sample should consist of a sufficiently large and random sample taken from the target population. If a test publisher has done an excellent job gathering a normative sample, the publisher will want you to know that. The simplest way to bring this information to your attention is a well-designed table. A table should highlight what is relevant and present the data in a format that is easy to understand. After all, the purpose of a table is to present complex information in a tidy format so you can further analyze what the author is saying.

What if there is no table in your test manual that shows the information you need to know? Maybe the statistical information you need is in the text, but chances are, if the data are not represented clearly in a table, they simply are not there. In this case, what is absent may speak as loudly as what is present.

One-Way versus Two-Way Tables

Here is a simple example of a one-way table. This is the simplest method for analyzing categorical (or nominal) data. It shows one kind of information about one variable. This kind of table is often used to explore data, for an initial look at what has been found. It is sometimes called a frequency table.

Here is a simple example of a two-way table. This is a combination of two (or more) one-way tables arranged such that each cell in the table represents a unique combination of information derived from the variables. Two-way tables allow examination of categories by frequencies of observations on more than one variable. By examining these frequencies, we can identify relationships between the variables.

Two Examples

Here is an example of a two-way table from the PPVT-4 manual. It is actually a composite of four one-way tables. There is a wealth of information presented about the ethnic breakdown of the PPVT-4 norming sample in this table. In this example the sample population is described by four broad ethnic groups, and the table clearly indicates where each portion of the sample was drawn from by region of the USA. Plus, how that portion of the sample compares to US demographics overall.

Here is another example of a 2-way table from the Comprehensive Assessment of Spoken Language (CASL). The table clearly reports the number (N) and percentage of females and males in the sample at each age range, with a comparison between the sample and the U.S. population as a whole at each age range. You can see clearly that the sample size was sufficiently large to be statistically reliable. Also the percentage of subjects in each age and gender group closely matched the percentage of persons in that category in the U.S. population. For example, 50.7 percent of the 14-15 year olds in the sample were female, which closely matched the Bureau of the Census figure of 50.9 percent of 14-15 year olds in the U.S. population. So this table shows the closeness of the normative population on age and sex, simultaneously, rather than just one or the other.

In Closing

Next time you shop for a test, look at the tables in the manual. The strength of the product should be easily seen in them. Look for the data in plain view. If it isn’t easy to find in a simple clear format, you should ask why.

Good tables may not be important to everyone in a restaurant, but good tables are paramount for everyone who evaluates, chooses and uses tests. It is also paramount in serving your clients.

References

Carrow-Woolfolk, E. (1999). Comprehensive Assessment of Spoken Language, Manual. Minneapolis, MN: Pearson Assessments.

Dunn, L.M., Dunn, D. M. (2007). Peabody Picture Vocabulary Test fourth edition, Manual. Minneapolis, MN: Pearson Assessments.

SLP Discussion Center

As always, we'd like to thank you for your ongoing service to people with communication needs and to remind you that we are here to support you in that effort. If you'd like to discuss this topic further, please feel free to use the SLP Discussion Center as the vehicle for an ongoing discussion with your colleagues. Should you have questions regarding these or other Pearson Speech and Language products, we welcome your phone calls at 800-627-7271 or use our web site at http://ags.pearsonassessments.com.