Final answer:
The statistic that 86 percent of unhappily married individuals who stayed in their marriage were mostly happy when re-interviewed five years later can be misleading. Different research methodologies and interpretations can lead to contradictory results. A cohort study comparing intact marriages to those that end in divorce after a specific time frame would provide more accurate divorce rates.
Step-by-step explanation:
When evaluating the statistic that 86 percent of unhappily married individuals who stayed in their marriage were mostly "very" or "quite" happy when re-interviewed five years later, it is important to note that different methodologies and interpretations can lead to contradictory results. The number of marriages in a given year does not directly correlate to the divorces occurring in that same year. Therefore, it is not accurate to state that exactly half of all marriages fail. Additionally, a cohort study comparing the percentage of intact marriages with those that end in divorce after a certain number of years would provide a more accurate measure of divorce rates.