Final answer:
The question asked is about finding the critical t-value for a 95% confidence interval with a sample size of 18, which is not directly given but can be found using a t-distribution table or statistical software for 17 degrees of freedom.
Step-by-step explanation:
The value of x² for a 95% confidence interval when n=18 is not directly provided but it refers to the critical value of the t-distribution for a given level of confidence and degrees of freedom (df), which in this case would be n - 1 or 17.
The question asked is about finding the critical t-value for a 95% confidence interval with a sample size of 18, which is not directly given but can be found using a t-distribution table or statistical software for 17 degrees of freedom.
To find the exact value, you would look up the critical t-value in a t-distribution table or use statistical software for df = 17 at a 95% confidence level. This critical t-value is used in calculating the confidence interval for the true population mean when the population standard deviation is unknown and the sample size is small (n < 30).