Statistics 227 Question

Question

2) Sec 8.1-8.2: Answer the following topic:

1. To compute confidence interval of MEAN, how to determine whether to use critical value z or t (using normal curve or student's t distribution.)
2. Briefly describe how to compute confidence interval of mean with population standard deviation given. You may use an example for your explanation.
3. Briefly describe how to compute confidence interval of mean without population standard deviation given. You may use an example for your explanation.

Answer 1

If the population is normal or the sample size is greater than or equal to 30 AND the population standard deviation is known, then use the critical z value, otherwise, use the critical t value.