What is the critical value t' for constructing a 90% confidence interval for a mean from a sample size of n=18 observations?

Explanation:

Given

--- sample

--- confidence interval

Required

Determine the critical value

Start by calculating the degrees of freedom (df)

Next, calculate the significance level

This gives:

Express percentage as decimal

Next, we look at the t table at

and

We have the critical value to be:

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