This is consistent with past research on the subject. The researchers determined that other measures such as sales were less valuable because of external factors such as the skill of the call center representative. This is a fair assessment because it separates the effectiveness of the ad from the effectiveness of the company's other activities. The use of time interval sampling is also appropriate, although this choice was only based on the slim body of previous literature on the subject. The impact of repetition in radio advertising could result in different results if the dependent variable was measured using continuous measurement.

The sampling used to gather the subjects was relatively poor. Only two radio stations were used in the measurement and they both had the same homogenous demographic. The study is therefore limited to ads placed on stations with that demographic. Stations with different demographics, for example younger or gender-specific, may see completely different results. The objective of the study was fairly broad in focus, yet the subjects were chosen to be fairly narrow. This despite the researchers mentioning in the introduction to their paper that radio stations typically have narrow, homogenous markets. The researchers should have expanded the scope of their study in order to derive more accurate results, given that they are attempting to isolate results based on society as a whole.

Moreover, the sampling size was insufficient. The researchers received an abundance of zero responses. They tried to account for this with a Tobit analysis. It would have been more effective had they simply increased the sample size. This may not have provided a different percentage of zero responses, but it would have yielded more positive responses. In advertising, zero responses are a valid response. It is important to advertisers to understand when their ads are effective and when they are...

A larger sample size would give enough positive responses to derive stronger information, while the value of the zero responses is retained.
The study, in general, is reliable and valid, although its scope was limited. Two of the three independent variables selected were shown to have a significant impact on the results. The third was also a valid variable to test because it is another component which the advertising company can control, and one basis on which ad rates can be determined. The subject group was limited. It did not reflect the broad market, and the researchers did not appear to recognize this limitation. The dependent variables chosen were appropriate to the direct action elicited in the advertisements used. It would have been a more valuable survey had more advertisements been studied with different types of direct actions elicited and measured.

Overall, the study was a good starting point. The researchers were able to set a reasonable framework for their study using variables appropriate to the target audience (advertisers). The research was limited in its scope and therefore limited in its usefulness to the broad market. However, the framework it provides can be used in future surveys to provide information more specific to different subjects, different direct actions and different dependent variables. The researchers identified some areas of future study but neglected to build on others.

There are many different independent variables that can impact the effectiveness of an advertising campaign. This study represents a valid starting point for some of these independent variables but should by no means be viewed as a comprehensive study that can be used externally.

Works Cited

Verhoef, Peter C.; Hoekstra, Janny C. & van Aalst, Marcel. (n.d.) the effectiveness of direct response radio commercials. European Journal of Marketing. 34, 1/2, 143-156.