Final answer:
An odds ratio of 9.0 means that living with children under the age of 10 increases the risk of developing the common cold by nine times compared to those not living with young children.
Step-by-step explanation:
The odds ratio of 9.0 in the case-control study suggests that individuals living with children under the age of 10 are nine times more likely to develop the common cold compared to those who do not live with young children. This indicates a strong association between the risk factor of living with young children and the likelihood of contracting the common cold. Since the odds ratio is significantly greater than one, it reflects an increased risk for the individuals exposed to this particular living condition.