To determine if we can say with 80% certainty that city I had at least 650 cases of flu among adults last month, we need to examine the lower bound of the 80% confidence interval for city I.

Here's the process to make this determination:

1. Identify the 80% Confidence Interval for City I:

   • The confidence interval will be represented by a range, with a lower bound and an upper bound.
   • If the lower bound of this interval is greater than or equal to 650, then we can be 80% confident that city I had at least 650 cases.

2. Check the Lower Bound:

   • If the figure shows the confidence interval, check the lower bound value.

Since I do not have the actual figure, I can guide you on how to interpret it:

• Look at the interval for city I on the graph.
• Identify the point that represents the sample mean (usually marked on the graph).
• Check the range that spans from the lower bound to the upper bound for city I.

Example Interpretation:

Assume the 80% confidence interval for city I is shown as $[700, 900]$:

• The lower bound here is 700.
• Since 700 is greater than 650, we can say with 80% certainty that city I had at least 650 cases of the flu last month.

If the lower bound is less than 650, then we cannot be 80% certain that the number of cases was at least 650.

Would you like any more details or have any questions?

Here are 5 more questions you might be interested in:

1. How do you calculate a confidence interval for a sample mean?
2. What does the width of a confidence interval indicate?
3. How does changing the confidence level affect the confidence interval?
4. What factors influence the width of a confidence interval?
5. Can you explain the difference between confidence intervals and prediction intervals?

Tip: When interpreting confidence intervals, always check the bounds to make sure they align with the question being asked about the data.