Independent random samples were selected from populations 1 and 2. The sample sizes, means, and variances are as follows:

a. Find a 90% confidence interval for the difference in the population means. What does the phrase "90% confident" mean?
b. Find a 99% confidence interval for the difference in the population means. Can you conclude that there is a difference in the two population means? Explain.

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Population Sample Size Sample Mean Sample Variance 64 64 2.9 0.83 5.1 1.67