How many fish in a lake have been tagged by previous researchers?

To estimate the minimum sample size needed for a 95% confidence interval with a given standard deviation and margin of error, you can use the formula: n = (Z * σ / E)^2 where n is the sample size, Z is the Z-score for a 95% confidence interval, σ is the standard deviation, and E is the margin of error. For a 95% confidence interval, the Z-score is 1.96 (based on the standard normal distribution). In this case, the standard deviation (σ) is 3, and the margin of error (E) is 0.6. n = (1.96 * 3 / 0.6)^2 n = (9.8 / 0.6)^2 n = (16.333)^2 n ≈ 266.89 Since you can't have a fraction of a fish, round up to the nearest whole number to find the minimum sample size: n ≈ 267 fish The wildlife researcher would need to catch and examine a minimum of 267 fish to estimate the number of tagged fish with a 95% confidence level, a standard deviation of 3, and a margin of error of ±0.6 fish with tags.