: Validity questions whether the research measured what it was actually intended to measure.

: A tracking study where multiple waves are conducted over time.

: A process of determining how much advertising is necessary to reach your target audience. There are three factors to consider. How many impressions will your ad receive or how often is it viewed. Reach measures how much of the target audience has been exposed to the advertisement. Finally, frequency measures how often the target audience was exposed to your ad.